Memory for an artificial neural network accelerator

ABSTRACT

A memory for an artificial neural network (ANN) accelerator is provided. The memory includes a first bank, a second bank and a bank selector. Each bank includes at least two word lines and a plurality of read word selectors. Each word line stores a plurality of words, and each word has a plurality of bytes. Each read word selector has a plurality of input ports and an output port, is coupled to a corresponding word in each word line, and is configured to select a byte of the corresponding word of a selected word line based on a byte select signal. The bank selector is coupled to the read word selectors of the first bank and the second bank, and configured to select a combination of read word selectors from at least one of the first bank and the second bank based on a bank select signal.

BACKGROUND

The present disclosure relates to computer systems. More particularly, the present disclosure relates to computer systems including artificial neural networks (ANNs).

ANNs, such as deep neural networks (DNNs), convolutional neural networks (CNNs), etc., are a popular solution to a wide array of challenging classification, recognition and regression problems. However, many ANNs require a large number of calculations involving a large number of filter weights and activations, which presents a significant challenge with respect to access, storage and performance, particularly for mobile and other power or storage-constrained devices. An ANN hardware accelerator accelerates these calculations, such as, for example, general matrix multiplication (GEMM) operations performed by DNNs, convolution operations performed by CNNs, etc.

CNNs typically do not perform native convolution operations due to the complicated dataflow and expensive datapaths that are required. Instead, native convolution operations are converted into GEMM operations, which are then executed more efficiently by a central processing unit (CPU), a specialized processor, an ANN accelerator that includes systolic multiply-and-accumulate (MAC) arrays, etc. For example, the filter weights and activations (i.e., input feature maps or IFMs) for a convolution layer of a CNN may be converted into an expanded format (e.g., IM2COL format), and then processed as GEMM operations by an ANN accelerator to generate output feature maps (OFMs). An activation or scaling function and a bias may be applied to the OFMs by the convolution layer or a separate activation layer, and then the OFMs are provided as the activations (i.e., IFMs) for the next layer of the CNN.

For correct data alignment, it is necessary to skew the frontier data vectors provided to the MAC arrays, which ensures that the correct operands coincide inside the pipelined array. This is achieved using a set of delay registers or flip-flop blocks, which cost power and circuit area proportional to the size of the MAC array. The cost of these delays is about N²−N flops for a square array of dimension N.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1A depicts an ANN, in accordance with an embodiment of the present disclosure.

FIG. 1B depicts a fully-connected layer calculation for a hidden layer of an ANN, in accordance with an embodiment of the present disclosure.

FIG. 1C depicts a data flow diagram for a MAC array, in accordance with an embodiment of the present disclosure.

FIG. 2A depicts a CNN, in accordance with an embodiment of the present disclosure.

FIG. 2B depicts a convolution operation within a convolutional layer of a CNN, in accordance with an embodiment of the present disclosure.

FIG. 2C depicts a converted convolutional operation for a CNN, in accordance with an embodiment of the present disclosure.

FIG. 2D depicts a data flow diagram for a MAC array, in accordance with an embodiment of the present disclosure.

FIG. 3A depicts a memory for an ANN accelerator, in accordance with an embodiment of the present disclosure.

FIG. 3B depicts a data flow diagram for a sequence of read operations from a memory of an ANN accelerator, in accordance with an embodiment of the present disclosure.

FIG. 3C depicts a multiplexer mapping diagram for a memory for an ANN accelerator, in accordance with an embodiment of the present disclosure.

FIG. 4A depicts a memory for an ANN accelerator, in accordance with an embodiment of the present disclosure.

FIG. 4B depicts a data flow diagram for a sequence of read operations from a memory of an ANN accelerator, in accordance with an embodiment of the present disclosure.

FIG. 4C depicts a multiplexer mapping diagram for a memory for an ANN accelerator, in accordance with an embodiment of the present disclosure.

FIG. 5A depicts a block diagram of a memory for an ANN accelerator, in accordance with an embodiment of the present disclosure.

FIG. 5B depicts a data flow diagram for a sequence of read operations from a memory of an ANN accelerator, in accordance with an embodiment of the present disclosure.

FIG. 5C depicts a multiplexer mapping diagram for a memory for an ANN accelerator, in accordance with an embodiment of the present disclosure.

FIG. 6A depicts a block diagram of a memory for an ANN accelerator, in accordance with an embodiment of the present disclosure.

FIG. 6B depicts a data flow diagram for a sequence of write operations to a memory of an ANN accelerator, in accordance with an embodiment of the present disclosure.

FIG. 6C depicts a block diagram of a memory for an ANN accelerator, in accordance with an embodiment of the present disclosure.

FIG. 6D depicts a data flow diagram for a sequence of read operations from a memory of an ANN accelerator, in accordance with an embodiment of the present disclosure.

FIG. 6E depicts a multiplexer mapping diagram for a memory for an ANN accelerator, in accordance with an embodiment of the present disclosure.

FIG. 7 depicts a block diagram of a system, in accordance with an embodiment of the present disclosure.

FIG. 8 depicts a block diagram of an ANN accelerator, in accordance with an embodiment of the present disclosure.

DETAILED DESCRIPTION

Embodiments of the present disclosure will now be described with reference to the drawing figures, in which like reference numerals refer to like parts throughout.

Embodiments of the present disclosure advantageously eliminate the delay registers or flip flop blocks in systolic MAC arrays by changing the way data is read from, or written to, the memory without adding complexity and area to SRAM memories.

In one embodiment, a memory for an ANN accelerator includes a first bank, a second bank and a bank selector. The first bank includes at least two word lines and a plurality of read word selectors, each word line stores a plurality of words, each word has a plurality of bytes, each read word selector has a plurality of input ports and an output port, each read word selector is coupled to a corresponding word in each word line, and each read word selector is configured to select a byte of the corresponding word of a selected word line based on a byte select signal. The second bank includes at least two word lines and a plurality of read word selectors, each word line stores a plurality of words, each word has a plurality of bytes, each read word selector has a plurality of input ports and an output port, each read word selector is coupled to a corresponding word in each word line, and each read word selector is configured to select a byte of the corresponding word of a selected word line based on the byte select signal. The bank selector is coupled to the outputs of the read word selectors of the first bank and the outputs of the read word selectors of the second bank, and is configured to select a combination of read word selectors from at least one of the first bank and the second bank based on a bank select signal.

An ANN models the relationships between input data or signals and output data or signals using a network of interconnected nodes that is trained through a learning process. The nodes are arranged into various layers, including, for example, an input layer, one or more hidden layers, and an output layer. The input layer receives input data, such as, for example, image data, and the output layer generates output data, such as, for example, a probability that the image data contains a known object. Each hidden layer provides at least a partial transformation of the input data to the output data. A DNN has multiple hidden layers in order to model complex, nonlinear relationships between input data and output data.

In a fully-connected, feedforward ANN, each node is connected to all of the nodes in the preceding layer, as well as to all of the nodes in the subsequent layer. For example, each input layer node is connected to each hidden layer node, each hidden layer node is connected to each input layer node and each output layer node, and each output layer node is connected to each hidden layer node. Additional hidden layers are similarly interconnected. Each connection has a weight value, and each node has an activation function, such as, for example, a linear function, a step function, a sigmoid function, a tanh function, a rectified linear unit (ReLU) function, etc., that determines the output of the node based on the weighted sum of the inputs to the node. The input data propagates from the input layer nodes, through respective connection weights to the hidden layer nodes, and then through respective connection weights to the output layer nodes.

More particularly, at each input node, input data is provided to the activation function for that node, and the output of the activation function is then provided as an input data value to each hidden layer node. At each hidden layer node, the input data value received from each input layer node is multiplied by a respective connection weight, and the resulting products are summed or accumulated into an activation value that is provided to the activation function for that node. The output of the activation function is then provided as an input data value to each output layer node. At each output layer node, the output data value received from each hidden layer node is multiplied by a respective connection weight, and the resulting products are summed or accumulated into an activation value that is provided to the activation function for that node. The output of the activation function is then provided as output data. Additional hidden layers may be similarly configured to process data.

A multi-layer perceptron (MLP) is an ANN that has an input layer, an output layer and one or more hidden layers. MLPs may be used for natural language processing applications, such as machine translation, speech recognition, etc. Other ANNs include recurrent neural networks (RNNs), long short-term memories (LSTMs), sequence-to-sequence models that include an encoder RNN and a decoder RNN, shallow neural networks, etc.

A CNN is a variation of an MLP that may be used for classification or recognition applications, such as image recognition, speech recognition, etc. A CNN has an input layer, an output layer and multiple hidden layers including convolutional layers, pooling layers, normalization layers, fully-connected layers, etc. Each convolutional layer applies a sliding dot product or cross-correlation to an input volume, applies an activation function to the results, and then provides the activation or output volume to the next layer. Convolutional layers typically use the ReLU function as the activation function. In certain embodiments, the activation function is provided in a separate activation layer, such as, for example, a ReLU layer. A pooling layer reduces the dimensions of the output volume received from the preceding convolutional layer, and may calculate an average or a maximum over small clusters of data, such as, for example, 2×2 matrices. In certain embodiments, a convolutional layer and a pooling layer may form a single layer of a CNN. The fully-connected layers follow the convolutional and pooling layers, and include a flatten layer and a classification layer, followed by a normalization layer that includes a normalization function, such as the SoftMax function. The output layer follows the last fully-connected layer; in certain embodiments, the output layer may include the normalization function.

FIG. 1A depicts ANN 10, in accordance with an embodiment of the present disclosure.

ANN 10 includes input layer 20, one or more hidden layers 30, 40, 50, etc., and output layer 60. Input layer 20 includes one or more input nodes 21, 22, 23, etc. Hidden layer 30 includes one or more hidden nodes 31, 32, 33, 34, 35, etc. Hidden layer 40 includes one or more hidden nodes 41, 42, 43, 44, 45, etc. Hidden layer 50 includes one or more hidden nodes 51, 52, 53, 54, 55, etc. Output layer 60 includes one or more output nodes 61, 62, etc. Generally, ANN 10 includes N hidden layers, input layer 20 includes “i” nodes, hidden layer 30 includes “j” nodes, hidden layer 40 includes “k” nodes, hidden layer 50 includes “m” nodes, and output layer 60 includes “o” nodes. Many variations of input, hidden and output layers are clearly possible, including hidden layers that are locally-connected, rather than fully-connected, to one another.

Training an ANN includes optimizing the connection weights between nodes by minimizing the prediction error of the output data until the ANN achieves a particular level of accuracy. One method is backpropagation, or backward propagation of errors, which iteratively and recursively determines a gradient descent with respect to the connection weights, and then adjusts the connection weights to improve the performance of the network.

FIG. 1B depicts a fully-connected layer calculation 200 for hidden layer 40 of ANN 10, in accordance with an embodiment of the present disclosure.

In this embodiment, ANN 10 includes input layer 20, hidden layers 30, 40 and 50, and output layer 60. Input layer 20 includes two input nodes, input nodes 21 and 22, hidden layer 30 includes four hidden nodes i.e., hidden nodes 31, 32, 33 and 34, hidden layer 40 includes four hidden nodes i.e., hidden nodes 41, 42, 43 and 44, hidden layer 50 includes four hidden nodes i.e., hidden nodes 51, 52, 53 and 54, and output layer 60 includes one output node, i.e., output node 61. Input nodes 21 and 22 are connected to, and send data to, hidden nodes 41, 42, 43 and 44, and output node 61 is connected to, and receives data from, hidden nodes 51, 52, 53 and 54. While the fully-connected layer calculation 200 for hidden layer 40 is discussed below, the same principles apply to the fully-connected layer calculations for hidden layers 30 and 50.

Hidden node 41 is connected to, and receives input data from, hidden nodes 31, 32, 33 and 34 of hidden layer 30, hidden node 42 is connected to, and receives input data from, hidden nodes 31, 32, 33 and 34 of hidden layer 30, hidden node 43 is connected to, and receives input data from, hidden nodes 31, 32, 33 and 34 of hidden layer 30, and hidden node 44 is connected to, and receives input data from, hidden nodes 31, 32, 33 and 34 of hidden layer 30. Hidden node 41 is connected to, and sends output data to, hidden nodes 51, 52, 53 and 54 of hidden layer 50, hidden node 42 is connected to, and sends output data to, hidden nodes 51, 52, 53 and 54 of hidden layer 50, hidden node 43 is connected to, and sends output data to, hidden nodes 51, 52, 53 and 54 of hidden layer 50, and hidden node 44 is connected to, and sends output data to, hidden nodes 51, 52, 53 and 54 of hidden layer 50.

Each hidden node 41, 42, 43 and 44 has a weight associated with each input connection. For hidden node 41, weight w¹ ₁ is associated with the input connection with hidden node 31, weight w¹ ₂ is associated with the input connection with hidden node 32, weight w¹ ₃ is associated with the input connection with hidden node 33, and weight w¹ ₄ is associated with the input connection with hidden node 34. For hidden node 42, weight w² ₁ is associated with the input connection with hidden node 31, weight w² ₂ is associated with the input connection with hidden node 32, weight w² ₃ is associated with the input connection with hidden node 33, and weight w² ₄ is associated with the input connection with hidden node 34. For hidden node 43, weight w³ ₁ is associated with the input connection with hidden node 31, weight w³ ₂ is associated with the input connection with hidden node 32, weight w³ ₃ is associated with the input connection with hidden node 33, and weight w³ ₄ is associated with the input connection with hidden node 34. For hidden node 44, weight w⁴ ₁ is associated with the input connection with hidden node 31, weight w⁴ ₂ is associated with the input connection with hidden node 32, weight w⁴ ₃ is associated with the input connection with hidden node 33, and weight w⁴ ₄ is associated with the input connection with hidden node 34. Weights w¹ ₁, w¹ ₂, w¹ ₃ and w¹ ₄ form weight set w² ₁, weights w² ₁, w² ₂, w² ₃ and w² ₄ form weight set w₂, weights w³ ₁, w³ ₂, w³ ₃ and w³ ₄ form weight set w₃, and weights w⁴ ₁, w⁴ ₂, w⁴ ₃ and w⁴ ₄ form weight set w₄.

Weight sets w₁, w₂, w₃ and w₄ may be formed into weight matrix 202, input data received from hidden layer 30 may be formed into IFM or converted input data matrix 204, and OFM or converted output data matrix 206 may be sent as output data to hidden layer 50. Fully-connected layer calculation 200 multiplies weight matrix 202 (4×4) by input data matrix 204 (4×1) to generate output data matrix 206 (4×1). An activation function and a bias may be applied to each element of converted output data matrix 206, which are then output to hidden layer 50 as an IFM or input data matrix. An activation function and bias may be applied after each element of output data matrix 206 has been calculated, or, alternatively, after all of the elements of converted output data matrix 206 have been calculated.

To multiply weight matrix 202 and input data matrix 204, a dot product is calculated for each weight matrix 202 row and input data matrix 204 column pair. Weight matrix 202 includes four rows, and input data matrix 204 includes a single column. Generally, for each element o_(i) of output data matrix 206, a dot product of the i^(th) row of weight matrix 202 and the single column of input data matrix 204 is calculated by multiplying each element w_(i,j) of the i^(th) row of weight matrix 202 with a corresponding element a_(j) of the single column of input data matrix 204 to generate an intermediate product, and accumulating the intermediate products into element o_(i) of output data matrix 206.

As depicted in FIG. 1B, the dot product for element o₁ of output data matrix 206 is calculated using the first row of weight matrix 202 and the single column of input data matrix 204, i.e., o₁ is equal to w¹ ₁·a₁+w¹ ₂·a₂+w¹ ₃·a₃+w¹ ₄·a₄. Similarly, the dot product for element o₂ of output data matrix 206 is calculated using the second row of weight matrix 202 and the single column of input data matrix 204, i.e., o₂ is equal to w² ₁·a₁+w² ₂·a₂+w² ₃·a₃+w² ₄·a₄, the dot product for element o₃ of output data matrix 206 is calculated using the third row of weight matrix 202 and the single column of input data matrix 204, i.e., o₃ is equal to w³ ₁·a₁+w³ ₂·a₂+w³ ₃·a₃+w³ ₄·a₄, and the dot product for element o₄ of output data matrix 206 is calculated using the fourth row of weight matrix 202 and the single column of input data matrix 204, i.e., o₄ is equal to w⁴ ₁·a₁+w⁴ ₂·a₂+w⁴ ₃·a₃+w⁴ ₄·a₄.

In one embodiment, the fully-connected layer calculations for ANNs executing on central processor units (CPUs), graphics processing units (GPUs), etc., may be implemented as generic matrix multiplication (GEMM) operations, which may leverage GEMM-optimized software libraries, or, alternatively, which may be implemented in a dedicated ANN hardware accelerator using an array of MAC units.

FIG. 1C depicts a data flow diagram 220 for MAC array 228, in accordance with an embodiment of the present disclosure.

As noted above, GEMM operations may be implemented in a dedicated ANN hardware accelerator using an array of MAC units. In this embodiment, MAC array 228 is a systolic, output stationary array that implements fully-connected layer calculation 200 using a single row of four MAC units m₁, m₂, m₃ and m₄. The orientation of transposed weight matrix 222, transposed input data matrix 224, and transposed output data matrix 226 relative to MAC array 228 simplifies illustration; other orientations are also contemplated. Each row of transposed weight matrix 222 corresponds to a column of weight matrix 202, the single row of transposed input data matrix 224 corresponds to the single column of input data matrix 204, and the single row of transposed output data matrix 226 corresponds to the single column of output data matrix 206.

Generally, elements from input data matrix 204 are read from local memory, enter MAC array 228 at left-edge MAC unit m₁, and propagate one MAC unit to the right at the beginning of each processing cycle. Similarly, elements from weight matrix 202 are read from local memory, and enter MAC array 228 at MAC units m₁, m₂, m₃ and m₄.

Each MAC unit calculates a dot product, between a row of weight matrix 202 and the single column of input data matrix 204, to generate an element of output data matrix 206. Generally, a MAC unit includes, inter alia, a multiplier, an adder and a storage register. Each MAC unit is reset by clearing or zeroing its storage register prior to, or at the start of, a new dot product calculation.

MAC unit m₁ calculates the dot product of the first row of weight matrix 202 (i.e., weight set w¹) and the first (and only) column of input data matrix 204 to generate element o₁ of output data matrix 206. During the first processing cycle, MAC unit m₁ receives a₁ and w¹ ₁ from local memory, multiplies a₁ and w¹ ₁ to generate an intermediate product, adds the intermediate product to the value stored in the storage register (i.e., 0), and stores the accumulated result back in the storage register. During the second processing cycle, MAC unit m₁ transmits a₁ to MAC unit m₂, receives a₂ and w¹ ₂ from local memory, multiplies a₂ and w¹ ₂ to generate an intermediate product, adds the intermediate product to the value stored in the storage register, and stores the accumulated result back in the storage register.

During the third processing cycle, MAC unit m₁ transmits a₂ to MAC unit m₂, receives a₃ and w¹ ₃ from local memory, multiplies a₃ and w¹ ₃ to generate an intermediate product, adds the intermediate product to the value stored in the storage register, and stores the accumulated result back in the storage register. During the fourth processing cycle, MAC unit m₁ transmits a₃ to MAC unit m₂, receives a₄ and w¹ ₄ from the local memory, multiplies a₄ and w¹ ₄ to generate an intermediate product, adds the intermediate product to the value stored in the storage register, stores the accumulated result back in the storage register, and then outputs the value stored in the storage register as element o₁. During the fifth processing cycle, MAC unit m₁ transmits a₄ to MAC unit m₂, and then waits for the next sequence of operations to begin.

MAC unit m₂ calculates the dot product of the second row of weight matrix 202 (i.e., weight set w²) and the first (and only) column of input data matrix 204 to generate element o₂ of output data matrix 206. During the first processing cycle, w² ₁ is read from local memory and stored in a delay register or flip flop block (“ff₁”). MAC unit m₂ does not receive any data because a₁ is not yet available from MAC unit m₁, and w² ₁ has been stored in the delay register ff₁. During the second processing cycle, MAC unit m₂ receives a₁ from MAC unit m₁ and w² ₁ from the delay register ff₁; w² ₂ is read from local memory and stored in the delay register ff₁ after w² ₁ has been accessed. MAC unit m₂ multiplies a₁ and w² ₁ to generate an intermediate product, adds the intermediate product to the value stored in the storage register (i.e., 0), and stores the accumulated result back in the storage register. During the third processing cycle, MAC unit m₂ transmits a₁ to MAC unit m₃, receives a₂ from MAC unit m₁, and receives w² ₂ from the delay register ff₁; w² ₃ is read from local memory and stored in the delay register ff₁ after w² ₂ has been accessed. MAC unit m₂ multiplies a₂ and w² ₂ to generate an intermediate product, adds the intermediate product to the value stored in the storage register, and stores the accumulated result back in the storage register.

During the fourth processing cycle, MAC unit m₂ transmits a₂ to MAC unit m₃, receives a₃ from MAC unit m₁, and receives w² ₃ from the delay register ff₁; w² ₄ is read from local memory and stored in the delay register after w² ₃ has been accessed. MAC unit m₂ multiplies a₃ and w² ₃ to generate an intermediate product, adds the intermediate product to the value stored in the storage register, and stores the accumulated result back in the storage register. During the fifth processing cycle, MAC unit m₂ transmits a₃ to MAC unit m₃, receives a₄ from MAC unit m₁, and receives w² ₄ from the delay register ff₁. MAC unit m₂ multiplies a₄ and w² ₄ to generate an intermediate product, adds the intermediate product to the value stored in the storage register, stores the accumulated result back in the storage register, and then outputs the value stored in the storage register as element o₂. During the sixth processing cycle, MAC unit m₂ transmits a₄ to MAC unit m₃, and then waits for the next sequence of operations to begin.

MAC unit m₃ calculates the dot product of the third row of weight matrix 202 (i.e., weight set w³) and the first (and only) column of input data matrix 204 to generate element o₃ of output data matrix 206. During the first processing cycle, w³ ₁ is read from local memory and stored in a first delay register ff₁. MAC unit m₃ does not receive any data because a₁ is not yet available from MAC unit m₂, and w³ ₁ has been stored in the first delay register ff₁. During the second processing cycle, w³ ₁ is transferred from the first delay register ff₁ to a second delay register ff₂, and w³ ₂ is then read from local memory and stored in the first delay register ff₁. MAC unit m₃ does not receive any data because a₁ is not yet available from MAC unit m₂, and w³ ₁ has been stored in the second delay register ff₂. During the third processing cycle, MAC unit m₃ receives a₁ from MAC unit m₂ and w³ ₁ from the second delay register ff₂; w³ ₂ is transferred from the first delay register ff₁ to the second delay register ff₂ after w³ ₁ has been accessed, and w³ ₃ is then read from local memory and stored in the first delay register ff₁. MAC unit m₃ multiplies a₁ and w³ ₁ to generate an intermediate product, adds the intermediate product to the value stored in the storage register (i.e., 0), and stores the accumulated result back in the storage register.

During the fourth processing cycle, MAC unit m₃ transmits a₁ to MAC unit m₄, receives a₂ from MAC unit m₂, and receives w³ ₂ from the second delay register ff₂; w³ ₃ is transferred to the second delay register ff₂ after w³ ₂ has been accessed, and w³ ₄ is then read from local memory and stored in the first delay register ff₁. MAC unit m₃ multiplies a₂ and w³ ₂ to generate an intermediate product, adds the intermediate product to the value stored in the storage register, and stores the accumulated result back in the storage register. During the fifth processing cycle, MAC unit m₃ transmits a₂ to MAC unit m₄, receives a₃ from MAC unit m₂, and receives w³ ₃ from the second delay register ff₂; w³ ₄ is transferred to the second delay register ff₂ after w³a has been accessed. MAC unit m₃ multiplies a₃ and w³ ₃ to generate an intermediate product, adds the intermediate product to the value stored in the storage register, and stores the accumulated result back in the storage register. During the sixth processing cycle, MAC unit m₃ transmits a₃ to MAC unit m₄, receives a₄ from MAC unit m₂, and receives w³ ₄ from the second delay register ff₂. MAC unit m₃ multiplies a₄ and w³ ₄ to generate an intermediate product, adds the intermediate product to the value stored in the storage register, stores the accumulated result back in the storage register, and then outputs the value stored in the storage register as element o₃. During the seventh processing cycle, MAC unit m₃ transmits a₄ to MAC unit m₄, and then waits for the next sequence of operations to begin.

MAC unit m₄ calculates the dot product of the fourth row of weight matrix 202 (i.e., weight set w⁴) and the first (and only) column of input data matrix 204 to generate element o₄ of output data matrix 206. During the first processing cycle, w⁴ ₁ is read from local memory and stored in a first delay register ff₁, and MAC unit m₄ does not receive any data because a₁ is not yet available from MAC unit m₃, and w⁴ ₁ has been stored in the first delay register ff₁. During the second processing cycle, w⁴ ₁ is transferred from the first delay register ff₁ to a second delay register ff₂, w⁴ ₂ is then read from local memory and stored in the first delay register ff₁, and MAC unit m₄ does not receive any data because a₁ is not yet available from MAC unit m₃, and w⁴ ₁ has been stored in the second delay register ff₂. During the third processing cycle, w⁴ ₁ is transferred from the second delay register ff₂ to a third delay register ff₃, w⁴ ₂ is transferred from the first delay register ff₁ to the second delay register ff₂, w⁴ ₃ is then read from local memory and stored in the first delay register ff₁, and MAC unit m₄ does not receive any data because a₁ is not yet available from MAC unit m₃, and w⁴ ₁ has been stored in the third delay register ff₃.

During the fourth processing cycle, MAC unit m₄ receives a₁ from MAC unit m₃ and w⁴ ₁ from the third delay register ff₃; w⁴ ₂ is transferred from the second delay register ff₂ to the third delay register ff₃ after w⁴ ₁ has been accessed, w⁴ ₃ is transferred from the first delay register ff₁ to the second delay register ff₂, and w⁴ ₄ is read from local memory and stored in the first delay register ff₁. MAC unit m₄ multiplies a₁ and w⁴ ₁ to generate an intermediate product, adds the intermediate product to the value stored in the storage register (i.e., 0), and stores the accumulated result back in the storage register.

During the fifth processing cycle, MAC unit m₄ receives a₂ from MAC unit m₃, and receives w⁴ ₂ from the third delay register ff₃; w⁴ ₃ is transferred from the second delay register ff₂ to the third delay register ff₃ after w⁴ ₂ has been accessed, and w⁴ ₄ is transferred from the first delay register ff₁ to the second delay register ff₂. MAC unit m₄ multiplies a₂ and w⁴ ₂ to generate an intermediate product, adds the intermediate product to the value stored in the storage register, and stores the accumulated result back in the storage register. During the sixth processing cycle, MAC unit m₄ receives a₃ from MAC unit m₃, and receives w⁴ ₃ from the third delay register ff₃; w⁴ ₄ is transferred from the second delay register ff₂ to the third delay register ff₃ after w³ ₃ has been accessed. MAC unit m₄ multiplies a₃ and w⁴ ₃ to generate an intermediate product, adds the intermediate product to the value stored in the storage register, and stores the accumulated result back in the storage register. During the seventh processing cycle, MAC unit m₄ receives a₄ from MAC unit m₃, and receives w³ ₄ from the third delay register ff₃. MAC unit m₄ multiplies a₄ and w⁴ ₄ to generate an intermediate product, adds the intermediate product to the value stored in the storage register, stores the accumulated result back in the storage register, and then outputs the value stored in the storage register as element o₄. During the eighth processing cycle, MAC unit m₃ waits for the next sequence of operations to begin.

Each column of weight matrix 202 (i.e., each row of transposed weight matrix 222) is read during a single processing cycle. The first column of weight matrix 202, i.e., w¹ ₁, w² ₁, w³ ₁ and w⁴ ₁, is read during the first processing cycle; w¹ ₁ is provided to MAC unit m₁, w² ₁ is provided to the first delay register for MAC unit m₂, w³ ₁ is provided to the first delay register for MAC unit m₃, and w⁴ ₁ is provided to the first delay register for MAC unit m₄. Similarly, the second column of weight matrix 202, i.e., w¹ ₂, w² ₂, w³ ₂ and w⁴ ₂, is read during the second processing cycle; w¹ ₂ is provided to MAC unit m₁, w² ₂ is provided to the first delay register for MAC unit m₂, w³ ₂ is provided to the first delay register for MAC unit m₃, and w⁴ ₂ is provided to the first delay register for MAC unit m₄. The third column of weight matrix 202, i.e., w¹ ₃, w² ₃, w³ ₃ and w⁴ ₃, is read during the third processing cycle; w¹ ₃ is provided to MAC unit m₁, w² ₃ is provided to the first delay register for MAC unit m₂, w³ ₃ is provided to the first delay register for MAC unit m₃, and w⁴ ₃ is provided to the first delay register for MAC unit m₄. And, the fourth column of weight matrix 202, i.e., w¹ ₄, w² ₄, w³ ₄ and w⁴ ₄, is read during the fourth processing cycle; w¹ ₄ is provided to MAC unit m₁, w² ₄ is provided to the first delay register for MAC unit m₂, w³ ₄ is provided to the first delay register for MAC unit m₃, and w⁴ ₄ is provided to the first delay register for MAC unit m₄.

FIG. 2A depicts CNN 15, in accordance with an embodiment of the present disclosure. CNN 15 includes input layer 20, one or more hidden layers, such as convolutional layer 30-1, pooling layer 30-2, hidden (flatten) layer 40, hidden (classification) layer 50, etc., and output layer 60. Many other variations of input, hidden and output layers are contemplated.

Input layer 20 includes one or more input nodes 21, etc., that present the input data, such as a color image, as an input volume to the first convolutional layer, e.g., convolutional layer 30-1. The input volume is a three-dimensional matrix that has a width, a height and a depth. For example, input data that represent a color image may be presented as an input volume that is 512 pixels×512 pixels×3 channels (red, green, blue); other input volume dimensions may also be used, such as 32×32×3, 64×64×3, 128×128×3, etc., 32×32×1, 64×64×1, 128×128×1, 512×512×1, etc.

Convolutional layer 30-1 is locally-connected to input layer 20, and includes a plurality of nodes that are connected to local regions in the input volume (not depicted for clarity). For a CNN that uses a standard convolution, each node computes a dot product between the node's weights and the respective local region of the input volume to generate one element of an output volume. An activation function and a bias may be applied to each element of the output volume, and the output volume is then provided as the input volume to the next layer. The activation function and bias may be applied by each convolutional layer node or by the nodes of a subsequent locally-connected layer, such as an ReLU layer.

Pooling layer 30-2 is locally-connected to convolutional layer 30-1, and includes a plurality of nodes that are connected to local regions in the input volume (not depicted for clarity). Pooling layer 30-2 also produces an output volume that is provided as the input volume to the subsequent layer, such as, for example, another convolutional layer 30-1, a flatten layer 40, etc. In certain embodiments, convolutional layer 30-1 and pooling layer 30-2 form a single hidden layer 30. Similarly, in certain embodiments, convolutional layer 30-1, a ReLU layer and pooling layer 30-2 form a single hidden layer 30. Generally, the output volumes of the convolutional and pooling layers may be described as output feature maps, and one or more single hidden layers 30 form a feature learning portion of CNN 15.

Hidden layer 40 is a “flatten” layer that is locally-connected to pooling layer 30-2, and includes one or more hidden (flatten) nodes 41, 42, 43, 44, 45, etc. Hidden (flatten) layer 40 “flattens” the output volume produced by the preceding pooling layer 30-2 into a column vector, which is provided to the subsequent, fully-connected hidden layer 50.

Hidden layer 50 is a classification layer that is fully-connected to hidden (flatten) layer 40, and includes one or more hidden (classification) nodes 51, 52, 53, 54, 55, etc.

Output layer 60 includes one or more output nodes 61, 62, etc., and is fully-connected to hidden (classification) layer 50. Fully-connected output layer 60 receives the classification results output by hidden (classification) layer 50, and each node outputs a predicted class score. A normalization function, such as a Softmax function, may be applied to the predicted class scores by output layer 60, or, alternatively, by an additional layer interposed between hidden (classification) layer 50 and output layer 60.

Similar to ANNs, training a CNN includes optimizing the connection weights between nodes by minimizing the prediction error of the output data until the CNN achieves a particular level of accuracy. As noted above, backpropagation may be used to iteratively and recursively determines a gradient descent with respect to the connection weights, and then adjusts the connection weights to improve the performance of the network. Matrix multiplication operations, and, more particularly, MAC operations, are used extensively by CNNs, as well as other ANNs.

FIG. 2B depicts convolution layer operation 201 within convolutional layer 30-1 of CNN 15, in accordance with an embodiment of the present disclosure.

A convolutional layer generally includes M filters, C input channels, C input feature maps (i.e., one input feature map for each input channel) and M output feature maps (i.e., one output feature map for each filter). Each filter has C weight sets (i.e., each filter has a weight set for each input channel), and is convolved across the input feature maps to produce an output feature map corresponding to that filter. Convolutional layers generally require the movement of large amounts of data, generate a significant computational load, and require buffers of considerable size to store intermediate values.

In this embodiment, convolutional layer 30-1 includes four weight matrices or filters 202, i.e., filter 202 ¹, 202 ², 202 ³ and 202 ⁴, one input channel, one input feature map 204 and four output feature maps 206, i.e., 206 ¹, 206 ², 206 ³ and 206 ⁴. Each filter 202 is convolved across input feature map 204 to produce an output feature map 206 corresponding to that filter, i.e., output feature map 206 ¹ corresponds to filter 202 ¹, output feature map 206 ² corresponds to filter 202 ², output feature map 206 ³ corresponds to filter 202 ³, and output feature map 206 ⁴ corresponds to filter 202 ⁴. For illustration purposes, each filter 202 ¹, 202 ², 202 ³ and 202 ⁴ is a 2×2×1 weight matrix, input feature map 204 is a 5×5×1 input data matrix, and each output feature map 206 ¹, 206 ², 206 ³ and 206 ⁴ is a 4×4 output data matrix. In this embodiment, with a stride of 1 and no padding, the total number of MAC operations performed by convolution layer operation 201 is (2×2×1)×(4×4)×4 or 256.

For ease of discussion, input feature map 204 may be divided into four overlapping portions or quadrants. The first quadrant (i.e., a_(q1)) includes the first and second rows, i.e., a₁ to a₅ and a₆ to a₁₀, the second quadrant (not shown for clarity) includes the second and third rows, i.e., a₆ to a₁₀ and a₁₁ to a₁₅, the third quadrant (not shown for clarity) includes the third and fourth rows, i.e., a₁₁ to a₁₅ and a₁₆ to a₂₀, and the fourth quadrant (not shown for clarity) includes the fourth and fifth rows, i.e., a₁₆ to a₂₀ and a₂₁ to a₂₅.

Similarly, output feature maps 206 may be divided into four, three dimensional portions or quadrants. The first quadrant (i.e., o_(q1)) includes the first row of each output feature map 206 ¹, 206 ², 206 ³ and 206 ⁴, i.e., o¹ ₁, o¹ ₂, o¹ ₃, o¹ ₄, o² ₁, o² ₂, o² ₃, o² ₄, o³ ₁, o³ ₂, o³ ₃, o³ ₄, o⁴ ₁, o⁴ ₂, o₃ and o⁴ ₄. The second quadrant (not shown for clarity) includes the second row of each output feature map 206 ¹, 206 ², 206 ³ and 206 ⁴, i.e., o¹ ₅, o¹ ₆, o¹ ₇, o¹ ₈, o² ₅, o² ₆, o² ₇, o² ₈, o³ ₅, o³ ₆, o³ ₇, o³ ₈, o⁴ ₅, o⁴ ₆, o⁴ ₇ and o⁴ ₈. The third quadrant (not shown for clarity) includes the third row of each output feature map 206 ¹, 206 ², 206 ³ and 206 ⁴, i.e., o¹ ₉, o¹ ₁₀, o¹ ₁₁, o¹ ₁₂, o² ₉, o² ₁₀, o² ₁₁, o² ₁₂, o³ ₉, o³ ₁₀, o³ ₁₁, o³ ₁₂, o⁴ ₉, o⁴ ₁₀, o⁴ ₁₁, and o⁴ ₁₂. The fourth quadrant (not shown for clarity) includes the fourth row of each output feature map 206 ¹, 206 ², 206 ³ and 206 ⁴, i.e., o¹ ₁₃, o¹ ₁₄, o¹ ₁₅, o¹ ₁₆, o² ₁₃, o² ₁₄, o² ₁₅, o² ₁₆, o³ ₁₃, o³ ₁₄, o³ ₁₅, o³ ₁₆, o⁴ ₁₃, o⁴ ₁₄, o⁴ ₁₅, and o⁴ ₁₆.

The convolution operations performed on the first quadrant (i.e., a_(q1)) Of input feature map 204 are now discussed in detail.

For output feature map 206 ¹, element o¹ ₁ is the dot product of filter 202 ¹ and the first block (i.e., a₁, a₂, a₆ and a₇) of the first quadrant a_(q1) of input feature map 204, element o¹ ₂ is the dot product of filter 202 ¹ and the second block (i.e., a₂, a₃, a₇ and as) of the first quadrant a_(q1) of input feature map 204, element o¹ ₃ is the dot product of filter 202 ¹ and the third block (i.e., a₃, a₄, a₈ and a₉) of the first quadrant a_(q1) of input feature map 204, and o¹ ₄ is the dot product of filter 202 ¹ and the fourth block (i.e., a₄, a₅, a₉ and a₁₀) of the first quadrant a_(q1) of input feature map 204.

More particularly, the dot product of filter 202 ¹ and the first block of the first quadrant a_(q1) is equal to w¹ ₁·a₁+w¹ ₂·a₂+w¹ ₃·a₆+w¹ ₄·a₇. The dot product of filter 202 ¹ and the second block of the first quadrant a_(q1) is equal to w¹ ₁·a₂+w¹ ₂·a₃+w¹ ₃·a₇+w¹ ₄·a₈. The dot product of filter 202 ¹ and the third block of the first quadrant a_(q1) is equal to w¹ ₁·a₃+w¹ ₂·a₄+w¹ ₃ as +w¹ ₄ as. The dot product of filter 202 ¹ and the fourth block of the first quadrant a_(q1) is equal to w¹ ₁·a₄+w¹ ₂·a₅+w¹ ₃·a₉+w¹ ₄·a₁₀.

For output feature map 206 ², element o₂₁ is the dot product of filter 202 ² and the first block (i.e., a₁, a₂, a₆ and a₇) of the first quadrant a_(q1) of input feature map 204, output feature map element o² ₂ is the dot product of filter 202 ² and the second block (i.e., a₂, a₃, a₇ and a₈) of the first quadrant a_(q1) of input feature map 204, output feature map element o² ₃ is the dot product of filter 202 ² and the third block (i.e., a₃, a₄, a₈ and a₉) of the first quadrant a_(q1) of input feature map 204, and output feature map element o² ₄ is the dot product of filter 202 ² and the fourth block (i.e., a₄, a₅, a₉ and a₁₀) of the first quadrant a_(q1) of input feature map 204.

More particularly, the dot product of filter 202 ² and the first block of the first quadrant a_(q1) is equal to w² ₁·a₁+w² ₂·a₂+w² ₃·a₆+w² ₄·a₇. The dot product of filter 202 ² and the second block of the first quadrant a_(q1) is equal to w² ₁·a₂+w² ₂·a₃+w² ₃·a₇+w² ₄·a₈. The dot product of filter 202 ² and the third block of the first quadrant a_(q1) is equal to w² ₁·a₃+w² ₂·a₄+w² ₃·a₆+w² ₄ as. The dot product of filter 202 ² and the fourth block of the first quadrant a_(q1) is equal to w² ₁·a₄+w² ₂·a₅+w² ₃·a₉+w² ₄·a₁₀.

For output feature map 206 ³, element o³ ₁ is the dot product of filter 202 ³ and the first block (i.e., a₁, a₂, a₆ and a₇) of the first quadrant a_(q1) of input feature map 204, output feature map element o³ ₂ is the dot product of filter 202 ³ and the second block (i.e., a₂, a₃, a₇ and a₈) of the first quadrant a_(q1) of input feature map 204, output feature map element o³ is the dot product of filter 202 ³ and the third block (i.e., a₃, a₄, a₈ and a₉) of the first quadrant a_(q1) of input feature map 204, and output feature map element o³ ₄ is the dot product of filter 202 ³ and the fourth block (i.e., a₄, a₅, a₉ and a₁₀) of the first quadrant a_(q1) of input feature map 204.

More particularly, the dot product of filter 202 ³ and the first block of the first quadrant a_(q1) is equal to w³ ₁·a₁+w³ ₂·a₂+w³ ₃·a₆+w³ ₄·a₇. The dot product of filter 202 ³ and the second block of the first quadrant a_(q1) is equal to w³ ₁·a₂+w³ ₂·a₃+w³·a₇+w³ ₄·a₈. The dot product of filter 202 ³ and the third block of the first quadrant a_(q1) is equal to w³ ₁·a₃+w³ ₂·a₄+w³ ₃a₆+w³ ₄ as. The dot product of filter 202 ³ and the fourth block of the first quadrant a_(q1) is equal to w³ ₁·a₄+w³ ₂·a₅+w³ ₃·a₉+w³ ₄·a₁₀.

For output feature map 206 ⁴, element o⁴ ₁ is the dot product of filter 202 ⁴ and the first block (i.e., a₁, a₂, a₆ and a₇) of the first quadrant a_(q1) of input feature map 204, output feature map element o₄₂ is the dot product of filter 202 ⁴ and the second block (i.e., a₂, a₃, a₇ and a₈) of the first quadrant a_(q1) of input feature map 204, output feature map element o₄₃ is the dot product of filter 202 ⁴ and the third block (i.e., a₃, a₄, a₈ and a₉) of the first quadrant a_(q1) of input feature map 204, and output feature map element o₄₄ is the dot product of filter 202 ⁴ and the fourth block (i.e., a₄, a₅, a₉ and a₁₀) of the first quadrant a_(q1) of input feature map 204.

More particularly, the dot product of filter 202 ⁴ and the first block of the first quadrant a_(q1) is equal to w⁴ ₁·a₁+w⁴ ₂·a₂+w⁴ ₃·a₆+w⁴ ₄·a₇. The dot product of filter 202 ⁴ and the second block of the first quadrant a_(q1) is equal to w⁴ ₁·a₂+w⁴ ₂·a₃+w⁴ ₃·a₇+w⁴ ₄·a₈. The dot product of filter 202 ⁴ and the third block of the first quadrant a_(q1) is equal to w⁴ ₁·a₃+w⁴ ₂·a₄+w⁴ ₃·a₈+w⁴ ₄·a₉. The dot product of filter 202 ⁴ and the fourth block of the first quadrant a_(q1) is equal to w⁴ ₁·a₄+w⁴ ₂·a₅+w⁴ ₃·a₉+w⁴ ₄·a₁₀.

The convolution operations performed on the remaining three quadrants of input feature map 204 are done in the same manner. The second quadrant of input feature map 204 also includes four blocks, i.e., the first block of includes a₆, a₇, a₁₁ and a₁₂, the second block includes a₇, a₈, a₁₂ and a₁₃, the third block includes a₈, a₉, a₁₃ and a₁₄, and the fourth block includes a₉, a₁₀, a₁₄ and a₁₅. The third quadrant of input feature map 204 also includes four blocks, i.e., the first block of includes a₁₁, a₁₂, a₁₆ and a₁₇, the second block includes a₁₂, a₁₃, a₁₇ and a₁₈, the third block includes a₁₃, a₁₄, a₁₈ and a₁₉, and the fourth block includes a₁₄, a₁₅, a₁₉ and a₂₀. The fourth quadrant of input feature map 204 also includes four blocks, i.e., the first block of includes a₁₆, a₁₇, a₂₁ and a₂₂, the second block includes a₁₇, a₁₈, a₂₂ and a₂₃, the third block includes a₁₈, a₁₉, a₂₃ and a₂₄, and the fourth block includes a₁₉, a₂₀, a₂₄ and a₂₅.

For the second quadrant of output feature map 206 ¹, element o¹ ₅ is the dot product of filter 202 ¹ and the first block of the second quadrant of input feature map 204, element o¹ ₆ is the dot product of filter 202 ¹ and the second block of the second quadrant of input feature map 204, element o¹ ₇ is the dot product of filter 202 ¹ and the third block of the second quadrant of input feature map 204, and element o¹ ₈ is the dot product of filter 202 ¹ and the fourth block of the second quadrant of input feature map 204. For the second quadrant of output feature map 206 ², elements o² ₅, o² ₆, o² ₇, and o² ₈ are calculated in the same manner using filter 202 ². For the second quadrant of output feature map 206 ³, elements o³ ₅, o³ ₆, o³ ₇, and o³ ₈ are calculated in the same manner using filter 202 ³. For the second quadrant of output feature map 206 ⁴, elements o⁴ ₅, o⁴ ₆, o⁴ ₇, and o⁴ ₈ are calculated in the same manner using filter 202 ⁴.

For the third quadrant of output feature map 206 ¹, element o¹ ₉ is the dot product of filter 202 ¹ and the first block of the third quadrant of input feature map 204, element o¹ ₁₀ is the dot product of filter 202 ¹ and the second block of the third quadrant of input feature map 204, element o¹ ₁₁ is the dot product of filter 202 ¹ and the third block of the third quadrant of input feature map 204, and element o¹ ₁₂ is the dot product of filter 202 ¹ and the fourth block of the third quadrant of input feature map 204. For the third quadrant of output feature map 206 ², elements o² ₉, o² ₁₀, o² ₁₁, and o² ₁₂ are calculated in the same manner using filter 202 ². For the third quadrant of output feature map 206 ³, elements o³ ₉, o³ ₁₀, o³ ₁₁, and o³ ₁₂ are calculated in the same manner using filter 202 ³. For the third quadrant of output feature map 206 ⁴, elements o⁴ ₉, o⁴ ₁₀, o⁴ ₁₁, and o⁴ ₁₂ are calculated in the same manner using filter 202 ⁴.

For the fourth quadrant of output feature map 206 ¹, element o¹ ₁₃ is the dot product of filter 202 ¹ and the first block of the fourth quadrant of input feature map 204, element o¹ ₁₄ is the dot product of filter 202 ¹ and the second block of the fourth quadrant of input feature map 204, element o¹ ₁₅ is the dot product of filter 202 ¹ and the third block of the fourth quadrant of input feature map 204, and element o¹ ₁₆ is the dot product of filter 202 ¹ and the fourth block of the fourth quadrant of input feature map 204. For the fourth quadrant of output feature map 206 ², elements o² ₁₃, o² ₁₄, o² ₁₅, and o² ₁₆ are calculated in the same manner using filter 202 ². For the fourth quadrant of output feature map 206 ³, elements o³ ₁₃, o³ ₁₄, o³ ₁₅, and o³ ₁₆ are calculated in the same manner using filter 202 ³. For the fourth quadrant of output feature map 206 ⁴, elements o⁴ ₁₃, o⁴ ₁₄, o⁴ ₁₅, and o⁴ ₁₆ are calculated in the same manner using filter 202 ⁴.

An activation function and a bias may be applied to each element of output feature maps 206, which are then provided as the input feature maps 204 to the next layer. An activation function and bias may be applied after each element of output feature maps 206 is calculated, after all of the elements of output feature maps 206 are calculated, or by a subsequent locally-connected layer, such as an ReLU layer.

Similar to the fully-connected layer calculations for ANNs, convolution operations may be recast as generic matrix multiplication (GEMM) operations, and implemented in an ANN hardware accelerator using an array of MAC units. The filter weights and activations (i.e., input feature maps or IFMs) for the convolution operation are converted into an expanded format (e.g., IM2COL format), and then processed as GEMM operations by the ANN hardware accelerator to generate output feature maps (OFMs).

FIG. 2C depicts a converted convolutional operation 211 within convolutional layer 30-1 of CNN 15, in accordance with an embodiment of the present disclosure.

In this embodiment, convolution layer operation 201 has been converted into a simple matrix multiplication operation by converting filter 202 into converted weight matrix 212, input feature map 204 into converted input data matrix 214, and output feature maps 206 into converted output data matrix 216. Converted weight matrix 212 (4×4) and converted input data matrix 214 (4×16) are multiplied to generate converted output data matrix 216 (4×16), which includes output data sets 216 ¹, 216 ², 216 ³ and 216 ⁴ (each 1×16). Output data sets 216 ¹, 216 ², 216 ³ and 216 ⁴ are then reformed into output feature maps 206 ¹, 206 ², 206 ³ and 206 ⁴ (each 4×4), respectively.

Converted weight matrix 212 includes converted weight sets 212 ¹, 212 ², 2123 and 2124. Converted weight set 212 ¹ includes the elements of filter 202 ¹, i.e., w¹ ₁, w¹ ₂, w¹ ₃ and w¹ ₄ arranged in a single (first) row. Converted weight set 212 ² includes the elements of filter 202 ², i.e., w² ₁, w² ₂, w² ₃ and w² ₄ arranged in a single (second) row. Converted weight set 2123 includes the elements of filter 202 ³, i.e., w³ ₁, w³ ₂, w³ ₃ and w³ ₄ arranged in a single (third) row. Converted weight set 2124 includes the elements of filter 202 ⁴, i.e., w⁴ ₁, w⁴ ₂, w⁴ ₃ and w⁴ ₄ arranged in a single (fourth) row.

Converted input data matrix 214 includes the elements of input feature map 204 recast as a larger matrix that implements the convolution operation as a simple matrix multiplication operation. Due to the mechanics of the convolution operation (discussed above), certain elements of input feature map 204 are duplicated once, twice or three times to generate converted output data matrix 216. Generally, each row of converted weight matrix 212 is a filter, each column of converted input data matrix 214 is a block of input data upon which each filter operates, and each dot product calculation, i.e., the multiplication of each row by each column, generates a different element of converted output data matrix 216.

For ease of discussion, converted input data matrix 214 may be divided into four portions or quadrants, i.e., a_(q1), a_(q2), a_(q3) and a_(q4), and converted output data matrix 216 may be divided into four portions or quadrants, i.e., o_(q1), o_(q2), o_(q3) and o_(q4).

The first quadrant a_(q1) of converted input data matrix 214 includes the four blocks of the first quadrant of input feature map 204, each block arranged as a column. Similarly, the second quadrant a_(q2) of converted input data matrix 214 includes the four blocks of the second quadrant of input feature map 204, each block arranged as a column. The third quadrant a_(q3) of converted input data matrix 214 includes the four blocks of the third quadrant of input feature map 204, each block arranged as a column. And, the fourth quadrant a_(q4) of converted input data matrix 214 includes the four blocks of the fourth quadrant of input feature map 204, each block arranged as a column.

More particularly, the first column of the first quadrant a_(q1) of converted input data matrix 214 includes elements a₁, a₂, a₆ and a₇, which are the same elements in the same sequence (i.e., row-major order) as the first block of the first quadrant of input feature map 204. The second column of the first quadrant a_(q1) of converted input data matrix 214 includes elements a₂, a₃, a₇ and a₈, which are the same elements in the same sequence (i.e., row-major order) as the second block of the first quadrant of input feature map 204. The third column of the first quadrant a_(q1) of converted input data matrix 214 includes elements a₃, a₄, a₈ and a₉, which are the same elements in the same sequence (i.e., row-major order) as the third block of the first quadrant of input feature map 204. The fourth column of the first quadrant a_(q1) of converted input data matrix 214 includes elements a₄, a₅, a₉ and a₁₀, which are the same elements in the same sequence (i.e., row-major order) as the fourth block of the first quadrant of input feature map 204. And so on for quadrants a_(q2), a_(q3) and a_(q4) of converted input data matrix 214.

The first row of the first quadrant o_(q1) of converted output data matrix 216 includes elements o¹ ₁, o¹, o¹ ₃ and o¹ ₄, which are the same elements in the same sequence as the first row of the first quadrant of output feature map 206 ¹. The second row of the first quadrant o_(q1) of converted output data matrix 216 includes elements o² ₁, o² ₂, o² ₃ and o² ₄, which are the same elements in the same sequence as the first row of the first quadrant of output feature map 206 ². The third row of the first quadrant o_(q1) of converted output data matrix 216 includes elements o³ ₁, o³ ₂, o³ ₃ and o³ ₄, which are the same elements in the same sequence as the first row of the first quadrant of output feature map 206 ³. The fourth row of the first quadrant o_(q1) of converted output data matrix 216 includes elements o⁴ ₁, o⁴ ₂, o⁴ ₃ and o⁴, which are the same elements in the same sequence as the first row of the first quadrant of output feature map 206 ⁴. And so on for quadrants o_(q2), o_(q3) and o_(q4) of converted output data matrix 216.

To generate the first quadrant o_(q1) of converted output data matrix 216, converted weight matrix 212 is multiplied by the first quadrant a_(q1) of converted input data matrix 214. For the first row of the first quadrant o_(q1), element o¹ ₁ is the dot product of the first row of converted weight matrix 212 and the first column of converted input data matrix 214, i.e., o¹ ₁ is equal to w¹ ₁·a₁+w¹ ₂·a₂+w¹ ₃·a₆+w¹ ₄·a₇. Element o¹ ₂ is the dot product of the first row of converted weight matrix 212 and the second column of converted input data matrix 214, i.e., o¹ ₂ is equal to w¹ ₁·a₂+w¹ ₂·a₃+w¹ ₃·a₇+w¹ ₄·a₈. Element o¹ ₃ is the dot product of the first row of converted weight matrix 212 and the third column of converted input data matrix 214, i.e., o¹ ₃ is equal to w¹ ₁·a₃+w¹ ₂ a₄+w¹ ₃·a₈+w¹ ₄·a₉. Element o¹ ₄ is the dot product of the first row of converted weight matrix 212 and the fourth column of converted input data matrix 214, i.e., o¹ ₄ is equal to w¹ ₁·a₄+w¹ ₂·a₅+w¹ ₃·a₈+w¹ ₄·a₁₀. The elements of the second, third and fourth rows the first quadrant o_(q1) of converted output data matrix 216, i.e., elements o² ₁, o² ₂, o² ₃, o² ₄, o³ ₁, o³ ₂, o³ ₃, o³ ₄, o⁴ ₁, o⁴ ₂, o³ ₃ and o⁴ ₄, are calculated in the same manner using the second, third and fourth rows of converted weight matrix 212, respectively.

To generate the second quadrant o_(q2) of converted output data matrix 216, converted weight matrix 212 is multiplied by the second quadrant a_(q2) of converted input data matrix 214. For the first row of the second quadrant o_(q2), element o¹ ₅ is the dot product of the first row of converted weight matrix 212 and the fifth column of converted input data matrix 214, i.e., o¹ ₅ is equal to w¹ ₁·a₆+w¹ ₂·a₇+w¹ ₃·a₁₁+w¹ ₄·a₁₂. Element o¹ ₆ is the dot product of the first row of converted weight matrix 212 and the sixth column of converted input data matrix 214, i.e., o¹ ₆ is equal to w¹ ₁·a₇+w¹ ₂·a₈+w¹ ₃·a₁₂+w¹ ₄·a₁₃. Element o¹ ₇ is the dot product of the first row of converted weight matrix 212 and the seventh column of converted input data matrix 214, i.e., o¹ ₇ is equal to w¹ ₁·a₈+w¹ ₂·a₉+w¹ ₃·a₁₃+w¹ ₄·a₁₄. Element o¹ ₈ is the dot product of the first row of converted weight matrix 212 and the eighth column of converted input data matrix 214, i.e., o¹ ₈ is equal to w¹ ₁·a₉+w¹ ₂·a₁₀+w¹ ₃·a₁₄+w¹ ₄·a₁₅. The elements of the second, third and fourth rows the second quadrant o_(q2) of converted output data matrix 216, i.e., elements o² ₅, o² ₆, o² ₇, o² ₈, o³ ₅, o³ ₆, o³ ₇, o³ ₈, o⁴ ₅, o⁴ ₆, o⁴ ₇ and o⁴ ₈, are calculated in the same manner using the second, third and fourth rows of converted weight matrix 212, respectively.

To generate the third quadrant o_(q3) of converted output data matrix 216, converted weight matrix 212 is multiplied by the third quadrant a_(q3) of converted input data matrix 214. For the first row of the third quadrant o_(q3), element o¹ ₉ is the dot product of the first row of converted weight matrix 212 and the ninth column of converted input data matrix 214, i.e., o¹ ₉ is equal to w¹ ₁·a₁₁+w¹ ₂·a₁₂+w¹ ₃·a₁₆+w¹ ₄·a₁₇. Element o¹ ₁₀ is the dot product of the first row of converted weight matrix 212 and the 10^(th) column of converted input data matrix 214, i.e., o¹ ₁₀ is equal to w¹ ₁·a₁₂+w¹ ₂·a₁₃+w¹ ₃·a₁₇+w¹ ₄·a₁₈. Element o¹ ₁₁ is the dot product of the first row of converted weight matrix 212 and the 11^(th) column of converted input data matrix 214, i.e., o¹ ₁₁ is equal to w¹ ₁·a₁₃+w¹ ₂·a₁₄+w¹ ₃·a₁₈+w¹ ₄·a₁₉. Element o¹ ₁₂ is the dot product of the first row of converted weight matrix 212 and the 12^(th) column of converted input data matrix 214, i.e., o¹ ₁₂ is equal to w¹ ₁·a₁₄+w¹ ₂·a₁₅+w¹ ₃·a₁₉+w¹ ₄·a₂₀. The elements of the second, third and fourth rows the third quadrant o_(q3) of converted output data matrix 216, i.e., elements o² ₉, o² ₁₀, o² ₁₁, o² ₁₂, o³ ₉, o³ ₁₀, o³ ₁₁, o³ ₁₂, o⁴ ₉, o⁴ ₁₀, o⁴ ₁₁ and o⁴ ₁₂, are calculated in the same manner using the second, third and fourth rows of converted weight matrix 212, respectively.

To generate the fourth quadrant o_(q4) of converted output data matrix 216, converted weight matrix 212 is multiplied by the fourth quadrant a_(q4) of converted input data matrix 214. For the first row of the fourth quadrant o_(q4), element o¹ ₁₃ is the dot product of the first row of converted weight matrix 212, and the 13^(th) column of converted input data matrix 214, i.e., o¹ ₁₃ is equal to w¹ ₁·a₁₆+w¹ ₂·a₁₇+w¹ ₃·a₂₁+w¹ ₄·a₂₂. Element o¹ ₁₄ is the dot product of the first row of converted weight matrix 212 and the 14^(th) column of converted input data matrix 214, i.e., o¹ ₁₄ is equal to w¹ ₁·a₁₇+w¹ ₂·a₁₈+w¹ ₃·a₂₂+w¹ ₄·a₂₃. Element o¹ ₁₅ is the dot product of the first row of converted weight matrix 212 and the 15^(th) column of converted input data matrix 214, i.e., o¹ ₁₅ is equal to w¹ ₁·a₁₈+w¹ ₂·a₁₉+w¹ ₃·a₂₃+w¹ ₄·a₂₄. Element o¹ ₁₆ is the dot product of the first row of converted weight matrix 212 and the 16^(th) column of converted input data matrix 214, i.e., o¹ ₁₆ is equal to w¹ ₁·a₁₉+w¹ ₂·a₂₀+w¹ ₃·a₂₄+w¹ ₄·a₂₅. The elements of the second, third and fourth rows the fourth quadrant o_(q4) of converted output data matrix 216, i.e., elements o² ₁₃, o² ₁₄, o² ₁₅, o² ₁₆, o³ ₁₃, o³ ₁₄, o³ ₁₅, o³ ₁₆, o⁴ ₁₃, o⁴ ₁₄, o⁴ ₁₅ and o⁴ ₁₆, are calculated in the same manner using the second, third and fourth rows of converted weight matrix 212, respectively.

FIG. 2D depicts a data flow diagram 221 for MAC array 228, in accordance with an embodiment of the present disclosure.

As noted above, GEMM operations may be implemented in a dedicated ANN hardware accelerator using an array of MAC units. In this embodiment, MAC array 228 is a systolic, output stationary array that implements converted convolution operation 211 using a 4×4 array of MAC units m₁, . . . , m₁₆. The orientation of transposed weight matrix 222, transposed input data matrix 224, and transposed output data matrix 226 relative to MAC array 228 simplifies illustration; other orientations are also contemplated.

As discussed above, each MAC unit calculates a dot product, between a row of converted weight matrix 212 and a column of converted input data matrix 214, to generate an element of converted output data matrix 216. Generally, a MAC unit includes, inter alia, a multiplier, an adder and a storage register. Each MAC unit is reset by clearing or zeroing its storage register prior to, or at the start of, a new dot product calculation.

Generally, elements from converted weight matrix 212 are read from local memory, enter MAC array 228 at the first row of MAC units m₁, m₂, m₃ and m₄, and propagate one MAC unit down at the beginning of each processing cycle. Similarly, elements from converted input data matrix 214 are read from local memory, enter MAC array 228 at the first column of MAC units m₁, m₅, m₉ and m₁₃, and propagate one MAC unit to the right at the beginning of each processing cycle. The dot product calculations performed by these edge MAC units are discussed in detail below, while the dot product calculations performed by the remaining MAC units in the second, third and fourth rows of MAC array 228 are summarized below.

MAC unit m₁ calculates the dot product of the first row of converted weight matrix 212 (i.e., converted weight set 212 ¹) and the first column of converted input data matrix 214 to generate element o¹ ₁ of converted output data matrix 216. During the first processing cycle, MAC unit m₁ receives a₁ and w¹ ₁ from local memory, multiplies a₁ and w¹ ₁ to generate an intermediate product, adds the intermediate product to the value stored in the storage register (i.e., 0), and stores the accumulated result back in the storage register. During the second processing cycle, MAC unit m₁ transmits a₁ to MAC unit m₂ and w¹ ₁ to MAC unit m₅, receives a₂ and w¹ ₂ from local memory, multiplies a₂ and w¹ ₂ to generate an intermediate product, adds the intermediate product to the value stored in the storage register, and stores the accumulated result back in the storage register.

During the third processing cycle, MAC unit m₁ transmits a₂ to MAC unit m₂ and w¹ ₂ to MAC unit m₅, receives a₃ and w¹ ₃ from local memory, multiplies a₃ and w¹ ₃ to generate an intermediate product, adds the intermediate product to the value stored in the storage register, and stores the accumulated result back in the storage register. During the fourth processing cycle, MAC unit m₁ transmits a₃ to MAC unit m₂ and w¹ ₃ to MAC unit m₅, receives a₄ and w¹ ₄ from the local memory, multiplies a₄ and w¹ ₄ to generate an intermediate product, adds the intermediate product to the value stored in the storage register, stores the accumulated result back in the storage register, and then outputs the value stored in the storage register as element o₁. During the fifth processing cycle, MAC unit m₁ transmits a₄ to MAC unit m₂ and w¹ ₄ to MAC unit m₅, and then waits for the next sequence of operations to begin.

MAC unit m₂ calculates the dot product of the second row of converted weight matrix 212 (i.e., converted weight set 212 ²) and the first column of converted input data matrix 214 to generate element o² ₁ of converted output data matrix 216. During the first processing cycle, w² ₁ is read from local memory and stored in delay register ff₁. MAC unit m₂ does not receive any data from MAC unit m₁ because a₁ is not yet available, and does not transmit any data to MAC unit m₆ because w² ₁ has been stored in the delay register ff₁. During the second processing cycle, MAC unit m₂ receives a₁ from MAC unit m₁ and w² ₁ from the delay register ff₁; w² ₂ is read from local memory and stored in the delay register ff₁ after w² ₁ has been accessed. MAC unit m₂ multiplies a₁ and w² ₁ to generate an intermediate product, adds the intermediate product to the value stored in the storage register (i.e., 0), and stores the accumulated result back in the storage register. During the third processing cycle, MAC unit m₂ transmits a₁ to MAC unit m₃ and w² ₁ to MAC unit m₆, receives a₂ from MAC unit m₁, and receives w² ₂ from the delay register ff₁; w² ₃ is read from local memory and stored in the delay register ff₁ after w² ₂ has been accessed. MAC unit m₂ multiplies a₂ and w² ₂ to generate an intermediate product, adds the intermediate product to the value stored in the storage register, and stores the accumulated result back in the storage register.

During the fourth processing cycle, MAC unit m₂ transmits a₂ to MAC unit m₃ and w² ₂ to MAC unit m₆, receives a₃ from MAC unit m₁, and receives w² ₃ from the delay register ff₁; w² ₄ is read from local memory and stored in the delay register ff₁ after w²a has been accessed. MAC unit m₂ multiplies a₃ and w² ₃ to generate an intermediate product, adds the intermediate product to the value stored in the storage register, and stores the accumulated result back in the storage register. During the fifth processing cycle, MAC unit m₂ transmits a₃ to MAC unit m₃ and w² ₃ to MAC unit m₆, receives a₄ from MAC unit m₁, and receives w² ₄ from the delay register ff₁. MAC unit m₂ multiplies a₄ and w² ₄ to generate an intermediate product, adds the intermediate product to the value stored in the storage register, stores the accumulated result back in the storage register, and then outputs the value stored in the storage register as element o₂. During the sixth processing cycle, MAC unit m₂ transmits a₄ to MAC unit m₃ and w² ₄ to MAC unit m₆, and then waits for the next sequence of operations to begin.

MAC unit m₃ calculates the dot product of the third row of converted weight matrix 212 (i.e., converted weight set 2123) and the first column of converted input data matrix 214 to generate element o³ ₁ of converted output data matrix 216. During the first processing cycle, w³ ₁ is read from local memory and stored in a first delay register ff₁. MAC unit m₃ does not receive any data from MAC unit m₂ because a₁ is not yet available, and does not transmit any data to MAC unit m₇ because w³ ₁ has been stored in the first delay register ff₁. During the second processing cycle, w³ ₁ is transferred from the first delay register ff₁ to a second delay register ff₂, and w³ ₂ is then read from local memory and stored in the first delay register ff₁. MAC unit m₃ does not receive any data from MAC unit m₂ because a₁ is not yet available, and does not transmit any data to MAC unit m₇ because w³ ₁ has been stored in the second delay register ff₂. During the third processing cycle, MAC unit m₃ receives a₁ from MAC unit m₂ and w³ ₁ from the second delay register ff₂; w³ ₂ is transferred from the first delay register ff₁ to the second delay register ff₂ after w³ ₁ has been accessed, and w³ ₃ is then read from local memory and stored in the first delay register ff₁. MAC unit m₃ multiplies a₁ and w³ ₁ to generate an intermediate product, adds the intermediate product to the value stored in the storage register (i.e., 0), and stores the accumulated result back in the storage register.

During the fourth processing cycle, MAC unit m₃ transmits a₁ to MAC unit m₄ and w³ ₁ to MAC unit m₇, receives a₂ from MAC unit m₂, and receives w³ ₂ from the second delay register ff₂; w³ ₃ is transferred to the second delay register ff₂ after w³ ₂ has been accessed, and w³ ₄ is then read from local memory and stored in the first delay register ff₁. MAC unit m₃ multiplies a₂ and w³ ₂ to generate an intermediate product, adds the intermediate product to the value stored in the storage register, and stores the accumulated result back in the storage register. During the fifth processing cycle, MAC unit m₃ transmits a₂ to MAC unit m₄ and w³ ₂ to MAC unit m₇, receives a₃ from MAC unit m₂, and receives w³ ₃ from the second delay register ff₂; w³ ₄ is transferred to the second delay register ff₂ after w³ ₃ has been accessed. MAC unit m₃ multiplies a₃ and w³ ₃ to generate an intermediate product, adds the intermediate product to the value stored in the storage register, and stores the accumulated result back in the storage register. During the sixth processing cycle, MAC unit m₃ transmits a₃ to MAC unit m₄ and w³ ₃ to MAC unit m₇, receives a₄ from MAC unit m₂, and receives w³ ₄ from the second delay register ff₂. MAC unit m₃ multiplies a₄ and w³ ₄ to generate an intermediate product, adds the intermediate product to the value stored in the storage register, stores the accumulated result back in the storage register, and then outputs the value stored in the storage register as element o₃. During the seventh processing cycle, MAC unit m₃ transmits a₄ to MAC unit m₄ and w³ ₄ to MAC unit m₇, and then waits for the next sequence of operations to begin.

MAC unit m₄ calculates the dot product of the fourth row of converted weight matrix 212 (i.e., converted weight set 2124) and the first column of converted input data matrix 214 to generate element o⁴ ₁ of converted output data matrix 216. During the first processing cycle, w⁴ ₁ is read from local memory and stored in a first delay register ff₁, and MAC unit m₄ does not receive any data from MAC unit m₃ because a₁ is not yet available, and w⁴ ₁ has been stored in the first delay register ff₁. During the second processing cycle, w⁴ ₁ is transferred from the first delay register ff₁ to a second delay register ff₂, w⁴ ₂ is then read from local memory and stored in the first delay register ff₁, and MAC unit m₄ does not receive any data from MAC unit m₃ because a₁ is not yet available, and w⁴ ₁ has been stored in the second delay register ff₂. During the third processing cycle, w⁴ ₁ is transferred from the second delay register ff₂ to a third delay register ff₃, w⁴ ₂ is transferred from the first delay register ff₁ to the second delay register ff₂, w⁴ ₃ is then read from local memory and stored in the first delay register ff₁, and MAC unit m₄ does not receive any data from MAC unit m₃ because a₁ is not yet available, and w⁴ ₁ has been stored in the third delay register ff₃.

During the fourth processing cycle, MAC unit m₄ receives a₁ from MAC unit m₃ and w⁴ ₁ from the third delay register ff₃; w⁴ ₂ is transferred from the second delay register ff₂ to the third delay register ff₃ after w⁴ ₁ has been accessed, w⁴ ₃ is transferred from the first delay register ff₁ to the second delay register ff₂, and w⁴ ₄ is read from local memory and stored in the first delay register ff₁. MAC unit m₄ multiplies a₁ and w⁴ ₁ to generate an intermediate product, adds the intermediate product to the value stored in the storage register (i.e., 0), and stores the accumulated result back in the storage register. During the fifth processing cycle, MAC unit m₄ transmits w⁴ ₁ to MAC unit m₈, receives a₂ from MAC unit m₃, and receives w⁴ ₂ from the third delay register ff₃; w⁴ ₃ is transferred from the second delay register ff₂ to the third delay register ff₃ after w⁴ ₂ has been accessed, and w⁴ ₄ is transferred from the first delay register ff₁ to the second delay register ff₂. MAC unit m₄ multiplies a₂ and w⁴ ₂ to generate an intermediate product, adds the intermediate product to the value stored in the storage register, and stores the accumulated result back in the storage register.

During the sixth processing cycle, MAC unit m₄ transmits w⁴ ₂ to MAC unit m₈, receives a₃ from MAC unit m₃, and receives w⁴ ₃ from the third delay register ff₃; w⁴ ₄ is transferred from the second delay register ff₂ to the third delay register ff₃ after w³ ₃ has been accessed. MAC unit m₄ multiplies a₃ and w⁴ ₃ to generate an intermediate product, adds the intermediate product to the value stored in the storage register, and stores the accumulated result back in the storage register. During the seventh processing cycle, MAC unit m₄ transmits w⁴ ₃ to MAC unit m₈, receives a₄ from MAC unit m₃, and receives w³ ₄ from the third delay register ff₃. MAC unit m₄ multiplies a₄ and w⁴ ₄ to generate an intermediate product, adds the intermediate product to the value stored in the storage register, stores the accumulated result back in the storage register, and then outputs the value stored in the storage register as element o⁴ ₁. During the eighth processing cycle, MAC unit m₄ transmits w⁴ ₄ to MAC unit m₈, and waits for the next sequence of operations to begin.

MAC unit m₅ calculates the dot product of the first row of converted weight matrix 212 (i.e., converted weight set 212 ¹) and the second column of converted input data matrix 214 to generate element o¹ ₂ of converted output data matrix 216. During the first processing cycle, a₂ is read from local memory and stored in a delay register ff₁. MAC unit m₅ does not receive any data from MAC unit m₁ because w¹ ₁ is not yet available, does not transmit any data to MAC unit m₆ because a₂ has been stored in the delay register ff₁, and does not transmit any data to MAC unit m₉ because w¹ ₁ is not yet available.

During the second processing cycle, MAC unit m₅ receives w¹ ₁ from MAC unit m₁ and a₂ from the delay register ff₁; a₃ is read from local memory and stored in the delay register ff₁ after a₂ has been accessed. MAC unit m₅ multiplies a₂ and w¹ ₁ to generate an intermediate product, adds the intermediate product to the value stored in the storage register (i.e., 0), and stores the accumulated result back in the storage register. During the third processing cycle, MAC unit m₅ transmits a₂ to MAC unit m₆ and w¹ ₁ to MAC unit m₉, receives w¹ ₂ from MAC unit m₁, and receives a₃ from the delay register ff₁; a₇ is read from local memory and stored in the delay register ff₁ after a₃ has been accessed. MAC unit m₅ multiplies a₃ and w¹ ₂ to generate an intermediate product, adds the intermediate product to the value stored in the storage register, and stores the accumulated result back in the storage register.

During the fourth processing cycle, MAC unit m₅ transmits a₃ to MAC unit m₆ and w¹ ₂ to MAC unit m₉, receives w¹ ₃ from MAC unit m₁, and receives a₇ from the delay register ff₁; as is read from local memory and stored in the delay register ff₁ after a₇ has been accessed. MAC unit m₅ multiplies a₇ and w¹ ₃ to generate an intermediate product, adds the intermediate product to the value stored in the storage register, and stores the accumulated result back in the storage register. During the fifth processing cycle, MAC unit m₅ transmits a₇ to MAC unit m₆ and w¹ ₃ to MAC unit m₉, receives w¹ ₄ from MAC unit m₁, and receives as from the delay register ff₁. MAC unit m₅ multiplies as and w¹ ₄ to generate an intermediate product, adds the intermediate product to the value stored in the storage register, stores the accumulated result back in the storage register, and then outputs the value stored in the storage register as element o¹ ₂. During the sixth processing cycle, MAC unit m₅ transmits as to MAC unit m₆ and w¹ ₄ to MAC unit m₉, and then waits for the next sequence of operations to begin.

The remainder of the second row of MAC array 228 includes MAC units m₆, m₇ and m₈. MAC unit m₆ receives weights from MAC unit m₂ and input data from MAC unit m₅, transmits weights to MAC unit m₁₀ and input data to MAC unit m₇, and calculates the dot product of the second row of converted weight matrix 212 (i.e., converted weight set 212 ²) and the second column of converted input data matrix 214 to generate element o² ₂ of converted output data matrix 216. MAC unit m₇ receives weights from MAC unit m₃ and input data from MAC unit m₆, transmits weights to MAC unit m₁₁ and input data to MAC unit m₈, and calculates the dot product of the third row of converted weight matrix 212 (i.e., converted weight set 2123) and the second column of converted input data matrix 214 to generate element o³ ₂ of converted output data matrix 216. MAC unit ma receives weights from MAC unit m₄ and input data from MAC unit m₇, transmits weights to MAC unit m₁₂, and calculates the dot product of the fourth row of converted weight matrix 212 (i.e., converted weight set 2124) and the second column of converted input data matrix 214 to generate element o⁴ ₂ of converted output data matrix 216.

MAC unit m₉ calculates the dot product of the first row of converted weight matrix 212 (i.e., converted weight set 212 ¹) and the third column of converted input data matrix 214 to generate element o¹ ₃ of converted output data matrix 216. During the first processing cycle, a₃ is read from local memory and stored in a first delay register ff₁. MAC unit m₉ does not receive any data from MAC unit m₅ because w¹ ₁ is not yet available, does not transmit any data to MAC unit m₁₀ because a₃ has been stored in the first delay register ff₁, and does not transmit any data to MAC unit m₁₃ because w¹ ₁ is not yet available.

During the second processing cycle, a₃ is transferred from the first delay register ff₁ to a second delay register ff₂, and a₄ is then read from local memory and stored in the first delay register ff₁. MAC unit m₉ does not receive any data from MAC unit m₅ because w¹ ₁ is not yet available, does not transmit any data to MAC unit m₁₀ because a₃ has been stored in the second delay register ff₂, and does not transmit any data to MAC unit m₁₃ because w¹ ₁ is not yet available. During the third processing cycle, MAC unit m₉ receives w¹ ₁ from MAC unit m₅ and a₃ from the second delay register ff₂; a₄ is transferred from the first delay register ff₁ to the second delay register ff₂ after a₃ has been accessed, and a₈ is then read from local memory and stored in the first delay register ff₁. MAC unit m₉ multiplies a₃ and w¹ ₁ to generate an intermediate product, adds the intermediate product to the value stored in the storage register (i.e., 0), and stores the accumulated result back in the storage register.

During the fourth processing cycle, MAC unit m₉ transmits w¹ ₁ to MAC unit m₁₃ and a₃ to MAC unit m₁₀, receives w¹ ₂ from MAC unit m₅, and receives a₄ from the second delay register ff₂; as is transferred to the second delay register ff₂ after a₄ has been accessed, and a₉ is then read from local memory and stored in the first delay register ff₁. MAC unit m₉ multiplies a₄ and w¹ ₂ to generate an intermediate product, adds the intermediate product to the value stored in the storage register, and stores the accumulated result back in the storage register. During the fifth processing cycle, MAC unit m₉ transmits w¹ ₂ to MAC unit m₁₃ and a₄ to MAC unit m₁₀, receives w¹ ₃ from MAC unit m₅, and receives as from the second delay register ff₂; as is transferred to the second delay register ff₂ after as has been accessed. MAC unit m₉ multiplies as and w¹ ₃ to generate an intermediate product, adds the intermediate product to the value stored in the storage register, and stores the accumulated result back in the storage register.

During the sixth processing cycle, MAC unit m₉ transmits w¹ ₃ to MAC unit m₁₃ and a₈ to MAC unit m₁₀, receives w¹ ₄ from MAC unit m₅, and receives as from the second delay register ff₂. MAC unit m₉ multiplies as and w¹ ₄ to generate an intermediate product, adds the intermediate product to the value stored in the storage register, stores the accumulated result back in the storage register, and then outputs the value stored in the storage register as element o¹ ₃. During the seventh processing cycle, MAC unit m₉ transmits as to MAC unit m₁₀ and w¹ ₄ to MAC unit m₁₃, and then waits for the next sequence of operations to begin.

The remainder of the third row of MAC array 228 includes MAC units m₁₀, m₁₁ and m₁₂. MAC unit m₁₀ receives weights from MAC unit m₆ and input data from MAC unit m₉, transmits weights to MAC unit m₁₄ and input data to MAC unit m₁₁, and calculates the dot product of the second row of converted weight matrix 212 (i.e., converted weight set 212 ²) and the third column of converted input data matrix 214 to generate element o² ₃ of converted output data matrix 216. MAC unit m₁ receives weights from MAC unit m₇ and input data from MAC unit m₁₀, transmits weights to MAC unit m₁₅ and input data to MAC unit m₁₂, and calculates the dot product of the third row of converted weight matrix 212 (i.e., converted weight set 2123) and the third column of converted input data matrix 214 to generate element o³ of converted output data matrix 216. MAC unit m₁₂ receives weights from MAC unit ma and input data from MAC unit m₁₁, transmits weights to MAC unit m₁₆, and calculates the dot product of the fourth row of converted weight matrix 212 (i.e., converted weight set 2124) and the third column of converted input data matrix 214 to generate element o⁴ ₃ of converted output data matrix 216.

MAC unit m₁₃ calculates the dot product of the first row of converted weight matrix 212 (i.e., converted weight set 212 ¹) and the fourth column of converted input data matrix 214 to generate element o¹ ₄ of converted output data matrix 216. During the first processing cycle, a₄ is read from local memory and stored in a first delay register ff₁, and MAC unit m₁₃ does not receive any data from MAC unit m₉ because w¹ ₁ is not yet available, and a₄ has been stored in the first delay register ff₁. During the second processing cycle, a₄ is transferred from the first delay register ff₁ to a second delay register ff₂, as is then read from local memory and stored in the first delay register ff₁, and MAC unit m₁₃ does not receive any data from MAC unit m₉ because w¹ ₁ is not yet available, and a₄ has been stored in the second delay register ff₂. During the third processing cycle, a₄ is transferred from the second delay register ff₂ to a third delay register ff₃, as is transferred from the first delay register ff₁ to the second delay register ff₂, as is then read from local memory and stored in the first delay register ff₁, and MAC unit m₁₃ does not receive any data from MAC unit m₉ because w¹ ₁ is not yet available, and a₄ has been stored in the third delay register ff₃.

During the fourth processing cycle, MAC unit m₁₃ receives w¹ ₁ from MAC unit m₉ and a₄ from the third delay register ff₃; as is transferred from the second delay register ff₂ to the third delay register ff₃ after a₄ has been accessed, as is transferred from the first delay register ff₁ to the second delay register ff₂, and a₁₀ is read from local memory and stored in the first delay register ff₁. MAC unit m₁₃ multiplies a₄ and w¹ ₁ to generate an intermediate product, adds the intermediate product to the value stored in the storage register (i.e., 0), and stores the accumulated result back in the storage register. During the fifth processing cycle, MAC unit m₁₃ transmits a₄ to MAC unit m₁₄, receives w¹ ₂ from MAC unit m₉, and receives as from the third delay register ff₃; as is transferred from the second delay register ff₂ to the third delay register ff₃ after as has been accessed, and a₁₀ is transferred from the first delay register ff₁ to the second delay register ff₂. MAC unit m₁₃ multiplies as and w¹ ₂ to generate an intermediate product, adds the intermediate product to the value stored in the storage register, and stores the accumulated result back in the storage register.

During the sixth processing cycle, MAC unit m₁₃ transmits a₅ to MAC unit m₁₄, receives w¹ ₃ from MAC unit m₉, and receives as from the third delay register ff₃; a₁₀ is transferred from the second delay register ff₂ to the third delay register ff₃ after as has been accessed. MAC unit m₁₃ multiplies as and w¹ ₃ to generate an intermediate product, adds the intermediate product to the value stored in the storage register, and stores the accumulated result back in the storage register. During the seventh processing cycle, MAC unit m₁₃ transmits as to MAC unit m₁₄, receives w¹ ₄ from MAC unit m₉, and receives a₁₀ from the third delay register ff₃. MAC unit m₁₃ multiplies a₁₀ and w¹ ₄ to generate an intermediate product, adds the intermediate product to the value stored in the storage register, stores the accumulated result back in the storage register, and then outputs the value stored in the storage register as element o¹ ₄. During the eighth processing cycle, MAC unit m₁₃ transmits a₁₀ to MAC unit m₉, and waits for the next sequence of operations to begin.

The remainder of the fourth row of MAC array 228 includes MAC units m₁₄, m₁₅ and m₁₆. MAC unit m₁₄ receives weights from MAC unit m₁₀ and input data from MAC unit m₁₃, transmits input data to MAC unit m₁₅, and calculates the dot product of the second row of converted weight matrix 212 (i.e., converted weight set 212 ²) and the fourth column of converted input data matrix 214 to generate element o² ₄ of converted output data matrix 216. MAC unit m₁₅ receives weights from MAC unit m₁₁ and input data from MAC unit m₁₄, transmits input data to MAC unit m₁₆, and calculates the dot product of the third row of converted weight matrix 212 (i.e., converted weight set 2123) and the fourth column of converted input data matrix 214 to generate element o³ ₄ of converted output data matrix 216. MAC unit m₁₆ receives weights from MAC unit m₁₂ and input data from MAC unit m₁₅, and calculates the dot product of the fourth row of converted weight matrix 212 (i.e., converted weight set 2124) and the fourth column of converted input data matrix 214 to generate element o⁴ ₄ of converted output data matrix 216.

After the first quadrant a_(q1) of converted input data matrix 214 has been processed, the next sequence of operations may begin in order to process the second quadrant a_(q2) of converted input data matrix 214. After the second quadrant a_(q2) of converted input data matrix 214 has been processed, the next sequence of operations may begin in order to process the third quadrant a_(q3) of converted input data matrix 214. And, after the third quadrant a_(q3) of converted input data matrix 214 has been processed, the final sequence of operations may begin in order to process the fourth quadrant a_(q4) of converted input data matrix 214. Converted weight matrix 212 is accessed for each sequence of operations.

In one embodiment, MAC array 228 may wait until the final element o⁴ ₄ of converted output data matrix 216 has been calculated at the end of the 10^(th) processing cycle before beginning the next sequence of operations for the next quadrant of converted input data matrix 214. In another embodiment, MAC array 228 may begin the next sequence of operations for the next quadrant of converted input data matrix 214 as soon as the first element o¹ ₁ of converted output data matrix 216 has been calculated at the end of the 4^(th) processing cycle. In this embodiment, MAC array 228 does not wait or suspend operations; instead, MAC array 228 continuously performs dot product calculations.

Each column of converted weight matrix 212 is read at the beginning of a processing cycle. The first column of converted weight matrix 212, i.e., weights w¹ ₁, w² ₁, w³ ₁ and w⁴ ₁, is read at the beginning of the first processing cycle; w¹ ₁ is provided to MAC unit m₁, w² ₁ is provided to the first delay register for MAC unit m₂, w³ ₁ is provided to the first delay register for MAC unit m₃, and w⁴ ₁ is provided to the first delay register for MAC unit m₄. Similarly, the second column of converted weight matrix 212, i.e., weights w¹ ₂, w² ₂, w³ ₂ and w⁴ ₂, is read at the beginning of the second processing cycle; w¹ ₂ is provided to MAC unit m₁, w² ₂ is provided to the first delay register for MAC unit m₂, w³ ₂ is provided to the first delay register for MAC unit m₃, and w⁴ ₂ is provided to the first delay register for MAC unit m₄. The third column of converted weight matrix 212, i.e., weights w¹ ₃, w² ₃, w³ ₃ and w⁴ ₃, is read at the beginning of the third processing cycle; w¹ ₃ is provided to MAC unit m₁, w² ₃ is provided to the first delay register for MAC unit m₂, w³ ₃ is provided to the first delay register for MAC unit m₃, and w⁴ ₃ is provided to the first delay register for MAC unit m₄. And, the fourth column of converted weight matrix 212, i.e., weights w¹ ₄, w² ₄, w³ ₄ and w⁴ ₄, is read at the beginning of the fourth processing cycle; w¹ ₄ is provided to MAC unit m₁, w² ₄ is provided to the first delay register for MAC unit m₂, w³ ₄ is provided to the first delay register for MAC unit m₃, and w⁴ ₄ is provided to the first delay register for MAC unit m₄.

Similarly, each row of a particular quadrant of converted input data matrix 214 is read at the beginning of a processing cycle. For example, the first row of the first quadrant a_(q1) of converted input data matrix 214, i.e., elements a₁, a₂, a₃ and a₄, is read at the beginning of the first processing cycle; a₁ is provided to MAC unit m₁, a₂ is provided to the first delay register for MAC unit m₅, a₃ is provided to the first delay register for MAC unit m₉, and a₄ is provided to the first delay register for MAC unit m₁₃. Similarly, the second row of the first quadrant a_(q1) of converted input data matrix 214, i.e., elements a₂, a₃, a₄ and a₅, is read at the beginning of the second processing cycle; a₂ is provided to MAC unit m₁, a₃ is provided to the first delay register for MAC unit m₅, a₄ is provided to the first delay register for MAC unit m₉, and a₅ is provided to the first delay register for MAC unit m₁₃. The third row of the first quadrant a_(q1) of converted input data matrix 214, i.e., elements a₆, a₇, a₈ and a₉, is read at the beginning of the third processing cycle; a₆ is provided to MAC unit m₁, a₇ is provided to the first delay register for MAC unit m₅, as is provided to the first delay register for MAC unit m₉, and a₉ is provided to the first delay register for MAC unit m₁₃. And, the fourth row of the first quadrant a_(q1) of converted input data matrix 214, i.e., elements a₇, a₈, a₉ and a₁₀, is read at the beginning of the fourth processing cycle; a₇ is provided to MAC unit m₁, as is provided to the first delay register for MAC unit m₅, as is provided to the first delay register for MAC unit m₉, and a₁₀ is provided to the first delay register for MAC unit m₁₃.

FIG. 3A depicts a block diagram 300 of a memory for an ANN accelerator, in accordance with an embodiment of the present disclosure.

Block diagram 300 depicts a portion of a memory, such as, for example, a conventional, 32-bit static random-access memory (SRAM). In this memory, the size of a word is 32 bits or 4 bytes. Four rows or word lines 310 are depicted for illustration purposes, i.e., word line 0, word line 1, word line 2 and word line 3. Each word line has four, 32-bit words 320, i.e., word 0, word 1, word 2 and word 3, and each 32-bit word has 4 bytes 330, i.e., b0, b1, b2 and b3.

Generally, a single access to a conventional 32-bit memory may only read (or write) a single word from (or to) a single row. A WordLineSelect signal identifies which row or word line 310 is to be accessed, such as, for example, word line 0, word line 1, word line 2, word line 3, etc. A column multiplexer 340 is coupled to the memory cells that store each word 320 of each word line 310, i.e., ColMux 0 is coupled to word 0 of word lines 0, 1, 2 and 3, ColMux 1 is coupled to word 1 of word lines 0, 1, 2 and 3, ColMux 2 is coupled to word 2 of word lines 0, 1, 2 and 3, and ColMux 3 is coupled to word 3 of word lines 0, 1, 2 and 3.

In this embodiment, column multiplexers 340 are associated with a memory read operation. Each “read” column multiplexer 340 has four 8-bit input ports and one 8-bit output port, and each input port is coupled to a different byte 330 of word 320, i.e., b0, b1, b2 or b3. A “read” ColMuxSelect signal identifies which input port of each column multiplexer 340 is to be selected, i.e., a value of 0 selects input port 0, a value of 1 selects input port 1, a value of 2 selects input port 2, and a value of 3 selects input port 3. The output port of each column multiplexer 340 outputs the value of the byte coupled to the selected input port, and the byte values are then formed into the word to be read, i.e., ColMux 0 provides the first byte, ColMux 1 provides the second byte, ColMux 2 provides the third byte, and ColMux 3 provides the fourth byte.

In this embodiment, each input port of each column multiplexer 340 is coupled to a different byte of the associated word as follows. For ColMux 0, input port 0 is coupled to b0 of word 0 of word lines 0, 1, 2 and 3, input port 1 is coupled to b1 of word 0 of word lines 0, 1, 2 and 3, input port 2 is coupled to b2 of word 0 of word lines 0, 1, 2 and 3, and input port 3 is coupled to b3 of word 0 of word lines 0, 1, 2 and 3. For ColMux 1, input port 0 is coupled to b0 of word 1 of word lines 0, 1, 2 and 3, input port 1 is coupled to b1 of word 1 of word lines 0, 1, 2 and 3, input port 2 is coupled to b2 of word 1 of word lines 0, 1, 2 and 3, and input port 3 is coupled to b3 of word 1 of word lines 0, 1, 2 and 3. For ColMux 2, input port 0 is coupled to b0 of word 2 of word lines 0, 1, 2 and 3, input port 1 is coupled to b1 of word 2 of word lines 0, 1, 2 and 3, input port 2 is coupled to b2 of word 2 of word lines 0, 1, 2 and 3, and input port 3 is coupled to b3 of word 2 of word lines 0, 1, 2 and 3. And, for ColMux 3, input port 0 is coupled to b0 of word 3 of word lines 0, 1, 2 and 3, input port 1 is coupled to b1 of word 3 of word lines 0, 1, 2 and 3, input port 2 is coupled to b2 of word 3 of word lines 0, 1, 2 and 3, and input port 3 is coupled to b3 of word 3 of word lines 0, 1, 2 and 3.

In one example, in response to a WordLineSelect signal of having a value of 0 and a ColMuxSelect signal of having a value of 0, word line 0 is selected, input port 0 of each column multiplexer 340 is selected, four bytes are read from the memory and a word is formed from b0 of word 0 of word line 0 (i.e., the output of ColMux 0), b0 of word 1 of word line 0 (i.e., the output of ColMux 1), b0 of word 2 of word line 0 (i.e., the output of ColMux 2), and b0 of word 3 of word line 0 (i.e., the output of ColMux 3).

For illustration purposes, converted input data matrix 214 has been stored in word lines 0, 1, 2 and 3 of the memory in column-order. Each word line 310 stores one quadrant of converted input data matrix 214, i.e., word line 0 stores quadrant a_(q1), word line 1 stores quadrant a_(q2), word line 2 stores quadrant a_(q3), and word line 3 stores quadrant a_(q4).

For word line 0, the elements of the first column of quadrant a_(q1) are stored in word 0, i.e., a₁, a₂, a₆ and a₇, the elements of the second column of quadrant a_(q1) are stored in word 1, i.e., a₂, a₃, a₇ and a₈, the elements of the third column of quadrant a_(q1) are stored in word 2, i.e., a₃, a₄, a₈ and a₉, and the elements of the fourth column of quadrant a_(q1) are stored in word 3, i.e., a₄, a₅, a₉ and a₁₀.

For word line 1, the elements of the first column of quadrant a_(q2) are stored in word 0, i.e., a₆, a₇, a₁₁ and a₁₂, the elements of the second column of quadrant a_(q2) are stored in word 1, i.e., a₇, a₈, a₁₂ and a₁₃, the elements of the third column of quadrant a_(q2) are stored in word 2, i.e., a₈, a₉, a₁₃ and a₁₄, and the elements of the fourth column of quadrant a_(q2) are stored in word 3, i.e., a₉, a₁₀, a₁₄ and a₁₅.

For word line 2, the elements of the first column of quadrant a_(q3) are stored in word 0, i.e., a₁₁, a₁₂, a₁₆ and a₁₇, the elements of the second column of quadrant a_(q3) are stored in word 1, i.e., a₁₂, a₁₃, a₁₇ and a₁₈, the elements of the third column of quadrant a_(q3) are stored in word 2, i.e., a₁₃, a₁₄, a₁₈ and a₁₉, and the elements of the fourth column of quadrant a_(q3) are stored in word 3, i.e., a₁₄, a₁₅, a₁₉ and a₂₀.

For word line 3, the elements of the first column of quadrant a_(q4) are stored in word 0, i.e., a₁₆, a₁₇, a₂₁ and a₂₂, the elements of the second column of quadrant a_(q4) are stored in word 1, i.e., a₁₇, a₁₈, a₂₂ and a₂₃, the elements of the third column of quadrant a_(q4) are stored in word 2, i.e., a₁₈, a₁₉, a₂₃ and a₂₄, and the elements of the fourth column of quadrant a_(q4) are stored in word 3, i.e., a₁₉, a₂₀, a₂₄ and a₂₅.

While converted input data matrix 214 has been depicted, converted weight matrix 212 may be similarly be stored in a different word line of the memory in row-order (rather than column-order), and similarly accessed for each quadrant of converted input data matrix 214. Converted weight set 212 ¹ (i.e., weights w¹ ₁, w¹ ₂, w¹ ₃ and w¹ ₄) may be stored in word 0, converted weight set 212 ² (i.e., weights w² ₁, w² ₂, w² ₃ and w² ₄) may be stored in word 1, converted weight set 2123 (i.e., weights w³ ₁, w³ ₂, w³ ₃ and w³ ₄) may be stored in word 2, and converted weight set 2124 (i.e., weights w⁴ ₁, w⁴ ₂, w⁴ ₃ and w⁴ ₄) may be stored in word 3.

In this embodiment, additional column multiplexers 350 (depicted in FIG. 3C; not depicted in FIG. 3A for clarity) may be associated with a memory write operation. Each “write” column multiplexer 350 has four 8-bit output ports and one 8-bit input port, and each output port is coupled to a different byte 330 of a respective word 320, i.e., b0, b1, b2 or b3. A “write” ColMuxSelect signal identifies which output port of each column multiplexer 350 is to be selected, i.e., a value of 0 selects output port 0, a value of 1 selects output port 1, a value of 2 selects output port 2, and a value of 3 selects output port 3. The input port of each column multiplexer 350 receives one byte of the word to be written, which is provided to the selected output port for writing to the memory cell, i.e., the first column multiplexer 350 receives and writes the first byte (“Byte 0”) to one of the bytes of word 0, the second column multiplexer 350 receives and writes the second byte (“Byte 1”) to one of the bytes of word 1, the third column multiplexer 350 receives and writes the third byte (“Byte 2”) to one of the bytes of word 2, and the fourth column multiplexer 350 receives and writes the fourth byte (“Byte 3”) to one of the bytes of word 3.

In this embodiment, each output port of each column multiplexer 350 is coupled to a different byte of the associated word as follows. For the first column multiplexer 350 (e.g., ColMux 0), input port 0 is coupled to b0 of word 0 of word lines 0, 1, 2 and 3, input port 1 is coupled to b1 of word 0 of word lines 0, 1, 2 and 3, input port 2 is coupled to b2 of word 0 of word lines 0, 1, 2 and 3, and input port 3 is coupled to b3 of word 0 of word lines 0, 1, 2 and 3. For the second column multiplexer 350 (e.g., ColMux 1), input port 0 is coupled to b0 of word 1 of word lines 0, 1, 2 and 3, input port 1 is coupled to b1 of word 1 of word lines 0, 1, 2 and 3, input port 2 is coupled to b2 of word 1 of word lines 0, 1, 2 and 3, and input port 3 is coupled to b3 of word 1 of word lines 0, 1, 2 and 3. For the third column multiplexer 350 (e.g., ColMux 2), input port 0 is coupled to b0 of word 2 of word lines 0, 1, 2 and 3, input port 1 is coupled to b1 of word 2 of word lines 0, 1, 2 and 3, input port 2 is coupled to b2 of word 2 of word lines 0, 1, 2 and 3, and input port 3 is coupled to b3 of word 2 of word lines 0, 1, 2 and 3. And, for the fourth column multiplexer 350 (e.g., ColMux 3), input port 0 is coupled to b0 of word 3 of word lines 0, 1, 2 and 3, input port 1 is coupled to b1 of word 3 of word lines 0, 1, 2 and 3, input port 2 is coupled to b2 of word 3 of word lines 0, 1, 2 and 3, and input port 3 is coupled to b3 of word 3 of word lines 0, 1, 2 and 3.

In one example, in response to a WordLineSelect signal of having a value of 0 and a “write” ColMuxSelect signal of having a value of 0, word line 0 is selected, output port 0 of each column multiplexer 350 is selected, four bytes are written to the memory, i.e., the first byte is written to b0 of word 0 of word line 0 (i.e., the output of ColMux 0), the second byte is written to b0 of word 1 of word line 0 (i.e., the output of ColMux 1), the third byte is written to b0 of word 2 of word line 0 (i.e., the output of ColMux 2), and the fourth byte is written to b0 of word 3 of word line 0 (i.e., the output of ColMux 3).

Other memory characteristics, such as, for example, different sized words (e.g., 64 bits, etc.), different numbers of column multiplexers (e.g., 2, 8, 16, etc.), etc., are also contemplated.

FIG. 3B depicts a data flow diagram 302 for a sequence of read operations from a memory of an ANN accelerator, in accordance with an embodiment of the present disclosure.

As described above, one row of a quadrant of converted input data matrix 214 is read at the beginning of each processing cycle when MAC array 228 continuously performs dot product calculations. Data flow diagram 302 depicts read cycles 1 to 16, which correspond to processing cycles 1 to 16 for converted convolution operation 211. While MAC unit m₁₆ does not complete the calculation of the last converted output data element o⁴ ₄ until processing cycle 22, only 16 read cycles are required to access all of the elements of converted input data matrix 214 from memory. Processing cycle 17 begins the sequence for a new converted convolution operation at read cycle 1, which accesses the first column of the first quadrant of the new converted input data matrix. MAC array 228 simultaneously performs dot product calculations for these two converted convolution operations during processing cycles 17 to 22, performs dot product calculations for the new converted convolution operation during processing cycles 23 to 32, and so on for each additional converted convolution operation.

With respect to converted convolution operation 211 described above, the first row of quadrant a_(q1) of converted input data matrix 214, i.e., elements a₁, a₂, a₃ and a₄, is read at the beginning of processing cycle 1, which corresponds to read cycle 1 depicted in FIG. 3B. For read cycle 1, the WordLineSelect signal is set to a value of 0, the ColMuxSelect signal is set to a value of 0, and the following bytes are selected and read from the memory by column multiplexers 340: b0 of word 0 of word line 0 (i.e., a₁) by ColMux 0, b0 of word 1 of word line 0 (i.e., a₂) by ColMux 1, b0 of word 2 of word line 0 (i.e., a₃) by ColMux 2, and b0 of word 3 of word line 0 (i.e., a₄) by ColMux 3.

The second row of quadrant a_(q1) of converted input data matrix 214, i.e., elements a₂, a₃, a₄ and a₅, is read at the beginning of processing cycle 2, which corresponds to read cycle 2 depicted in FIG. 3B. For read cycle 2, the WordLineSelect signal is set to a value of 0, the ColMuxSelect signal is set to a value of 1, and the following bytes are selected and read from the memory by column multiplexers 340: b1 of word 0 of word line 0 (i.e., a₂) by ColMux 0, b1 of word 1 of word line 0 (i.e., a₃) by ColMux 1, b1 of word 2 of word line 0 (i.e., a₄) by ColMux 2, and b1 of word 3 of word line 0 (i.e., a₅) by ColMux 3.

The third row of quadrant a_(q1) of converted input data matrix 214, i.e., elements a₆, a₇, a₈ and a₉, is read at the beginning of processing cycle 3, which corresponds to read cycle 3 depicted in FIG. 3B. For read cycle 3, the WordLineSelect signal is set to a value of 0, the ColMuxSelect signal is set to a value of 2, and the following bytes are selected and read from the memory by column multiplexers 340: b2 of word 0 of word line 0 (i.e., a₆) by ColMux 0, b2 of word 1 of word line 0 (i.e., a₇) by ColMux 1, b2 of word 2 of word line 0 (i.e., as) by ColMux 2, and b2 of word 3 of word line 0 (i.e., a₉) by ColMux 3.

The fourth row of quadrant a_(q1) of converted input data matrix 214, i.e., elements a₇, a₈, a₉ and a₁₀, is read at the beginning of processing cycle 4, which corresponds to read cycle 4 depicted in FIG. 3B. For read cycle 4, the WordLineSelect signal is set to a value of 0, the ColMuxSelect signal is set to a value of 3, and the following bytes are selected and read from the memory by column multiplexers 340: b3 of word 0 of word line 0 (i.e., a₇) by ColMux 0, b3 of word 1 of word line 0 (i.e., a₈) by ColMux 1, b3 of word 2 of word line 0 (i.e., a₉) by ColMux 2, and b3 of word 3 of word line 0 (i.e., a₁₀) by ColMux 3.

The first row of quadrant a_(q2) of converted input data matrix 214, i.e., elements a₆, a₇, a₈ and a₉, is read at the beginning of processing cycle 5, which corresponds to read cycle 5 depicted in FIG. 3B. For read cycle 5, the WordLineSelect signal is set to a value of 1, the ColMuxSelect signal is set to a value of 0, and the following bytes are selected and read from the memory by column multiplexers 340: b0 of word 0 of word line 1 (i.e., a₆) by ColMux 0, b0 of word 1 of word line 1 (i.e., a₇) by ColMux 1, b0 of word 2 of word line 1 (i.e., as) by ColMux 2, and b0 of word 3 of word line 1 (i.e., a₉) by ColMux 3.

The second row of quadrant a_(q2) of converted input data matrix 214, i.e., elements a₇, a₈, a₉ and a₁₀, is read at the beginning of processing cycle 6, which corresponds to read cycle 6 depicted in FIG. 3B. For read cycle 6, the WordLineSelect signal is set to a value of 1, the ColMuxSelect signal is set to a value of 1, and the following bytes are selected and read from the memory by column multiplexers 340: b1 of word 0 of word line 1 (i.e., a₇) by ColMux 0, b1 of word 1 of word line 1 (i.e., as) by ColMux 1, b1 of word 2 of word line 1 (i.e., a₉) by ColMux 2, and b1 of word 3 of word line 1 (i.e., a₁₀) by ColMux 3.

The third row of quadrant a_(q2) of converted input data matrix 214, i.e., elements a₁₁, a₁₂, a₁₃ and a₁₄, is read at the beginning of processing cycle 7, which corresponds to read cycle 7 depicted in FIG. 3B. For read cycle 7, the WordLineSelect signal is set to a value of 1, the ColMuxSelect signal is set to a value of 2, and the following bytes are selected and read from the memory by column multiplexers 340: b2 of word 0 of word line 1 (i.e., a₁₁) by ColMux 0, b2 of word 1 of word line 1 (i.e., a₁₂) by ColMux 1, b2 of word 2 of word line 1 (i.e., a₁₃) by ColMux 2, and b2 of word 3 of word line 1 (i.e., a₁₄) by ColMux 3.

The fourth row of quadrant a_(q2) of converted input data matrix 214, i.e., elements a₁₂, a₁₃, a₁₄ and a₁₅, is read at the beginning of processing cycle 8, which corresponds to read cycle 8 depicted in FIG. 3B. For read cycle 8, the WordLineSelect signal is set to a value of 1, the ColMuxSelect signal is set to a value of 3, and the following bytes are selected and read from the memory by column multiplexers 340: b3 of word 0 of word line 1 (i.e., a₁₂) by ColMux 0, b3 of word 1 of word line 1 (i.e., a₁₃) by ColMux 1, b3 of word 2 of word line 1 (i.e., a₁₄) by ColMux 2, and b3 of word 3 of word line 1 (i.e., a₁₅) by ColMux 3.

The first row of quadrant a_(q3) of converted input data matrix 214, i.e., elements a₁₁, a₁₂, a₁₃ and a₁₄, is read at the beginning of processing cycle 9, which corresponds to read cycle 9 depicted in FIG. 3B. For read cycle 9, the WordLineSelect signal is set to a value of 2, the ColMuxSelect signal is set to a value of 0, and the following bytes are selected and read from the memory by column multiplexers 340: b0 of word 0 of word line 2 (i.e., a₁₁) by ColMux 0, b0 of word 1 of word line 2 (i.e., a₁₂) by ColMux 1, b0 of word 2 of word line 2 (i.e., a₁₃) by ColMux 2, and b0 of word 3 of word line 2 (i.e., a₁₄) by ColMux 3.

The second row of quadrant a_(q3) of converted input data matrix 214, i.e., elements a₁₂, a₁₃, a₁₄ and a₁₅, is read at the beginning of processing cycle 10, which corresponds to read cycle 10 depicted in FIG. 3B. For read cycle 10, the WordLineSelect signal is set to a value of 2, the ColMuxSelect signal is set to a value of 1, and the following bytes are selected and read from the memory by column multiplexers 340: b1 of word 0 of word line 2 (i.e., a₁₂) by ColMux 0, b1 of word 1 of word line 2 (i.e., a₁₃) by ColMux 1, b1 of word 2 of word line 2 (i.e., a₁₄) by ColMux 2, and b1 of word 3 of word line 2 (i.e., a₁₅) by ColMux 3.

The third row of quadrant a_(q3) of converted input data matrix 214, i.e., elements a₁₆, a₁₇, a₁₈ and a₁₉, is read at the beginning of processing cycle 11, which corresponds to read cycle 11 depicted in FIG. 3B. For read cycle 11, the WordLineSelect signal is set to a value of 2, the ColMuxSelect signal is set to a value of 2, and the following bytes are selected and read from the memory by column multiplexers 340: b2 of word 0 of word line 2 (i.e., a₁₆) by ColMux 0, b2 of word 1 of word line 2 (i.e., a₁₇) by ColMux 1, b2 of word 2 of word line 2 (i.e., a₁₈) by ColMux 2, and b2 of word 3 of word line 2 (i.e., a₁₉) by ColMux 3.

The fourth row of quadrant a_(q3) of converted input data matrix 214, i.e., elements a₁₇, a₁₈, a₁₉ and a₂₀, is read at the beginning of processing cycle 12, which corresponds to read cycle 12 depicted in FIG. 3B. For read cycle 12, the WordLineSelect signal is set to a value of 2, the ColMuxSelect signal is set to a value of 3, and the following bytes are selected and read from the memory by column multiplexers 340: b3 of word 0 of word line 2 (i.e., a₁₇) by ColMux 0, b3 of word 1 of word line 2 (i.e., a₁₈) by ColMux 1, b3 of word 2 of word line 2 (i.e., a₁₉) by ColMux 2, and b3 of word 3 of word line 2 (i.e., a₂₀) by ColMux 3.

The first row of quadrant a_(q4) of converted input data matrix 214, i.e., elements a₁₆, a₁₇, a₁₈ and a₁₉, is read at the beginning of processing cycle 13, which corresponds to read cycle 13 depicted in FIG. 3B. For read cycle 13, the WordLineSelect signal is set to a value of 3, the ColMuxSelect signal is set to a value of 0, and the following bytes are selected and read from the memory by column multiplexers 340: b0 of word 0 of word line 3 (i.e., a₁₆) by ColMux 0, b0 of word 1 of word line 3 (i.e., a₁₇) by ColMux 1, b0 of word 2 of word line 3 (i.e., a₁₈) by ColMux 2, and b0 of word 3 of word line 3 (i.e., a₁₉) by ColMux 3.

The second row of quadrant a_(q4) of converted input data matrix 214, i.e., elements a₁₇, a₁₈, a₁₉ and a₂₀, is read at the beginning of processing cycle 14, which corresponds to read cycle 14 depicted in FIG. 3B. For read cycle 14, the WordLineSelect signal is set to a value of 3, the ColMuxSelect signal is set to a value of 1, and the following bytes are selected and read from the memory by column multiplexers 340: b1 of word 0 of word line 3 (i.e., a₁₇) by ColMux 0, b1 of word 1 of word line 3 (i.e., a₁₈) by ColMux 1, b1 of word 2 of word line 3 (i.e., a₁₉) by ColMux 2, and b1 of word 3 of word line 3 (i.e., a₁₂₀) by ColMux 3.

The third row of quadrant a_(q4) of converted input data matrix 214, i.e., elements a₂₁, a₂₂, a₂₃ and a₂₄, is read at the beginning of processing cycle 15, which corresponds to read cycle 15 depicted in FIG. 3B. For read cycle 15, the WordLineSelect signal is set to a value of 3, the ColMuxSelect signal is set to a value of 2, and the following bytes are selected and read from the memory by column multiplexers 340: b2 of word 0 of word line 3 (i.e., a₂₁) by ColMux 0, b2 of word 1 of word line 3 (i.e., a₂₂) by ColMux 1, b2 of word 2 of word line 3 (i.e., a₂₃) by ColMux 2, and b2 of word 3 of word line 3 (i.e., a₂₄) by ColMux 3.

The fourth row of quadrant a_(q4) of converted input data matrix 214, i.e., elements a₂₂, a₂₃, a₂₄ and a₂₅, is read at the beginning of processing cycle 16, which corresponds to read cycle 16 depicted in FIG. 3B. For read cycle 16, the WordLineSelect signal is set to a value of 3, the ColMuxSelect signal is set to a value of 3, and the following bytes are selected and read from the memory by column multiplexers 340: b3 of word 0 of word line 3 (i.e., a₂₂) by ColMux 0, b3 of word 1 of word line 3 (i.e., a₂₃) by ColMux 1, b3 of word 2 of word line 3 (i.e., a₂₄) by ColMux 2, and b3 of word 3 of word line 3 (i.e., a₂₅) by ColMux 3.

FIG. 3C depicts a word selector or multiplexer mapping diagram 304 for a memory for an ANN accelerator, in accordance with an embodiment of the present disclosure.

As described above, the memory may include four column multiplexers 340 associated with read operations, and four column multiplexers 350 associated with write operations. Multiplexer mapping diagram 304 illustrates the mapping between the “read” ColMuxSelect signal values (i.e., 0, 1, 2 and 3) and the bytes 330 of each word 320, as well as the mapping between the “write” ColMuxSelect signal values (i.e., 0, 1, 2 and 3) and the bytes 330 of each word 320.

A “read” ColMuxSelect signal value of 0 selects input port 0 of each column multiplexer 340, and, as illustrated in FIG. 3C, each input port 0 of each column multiplexer 340 is coupled 342 to byte 0 of word 0, 1, 2 or 3. A “read” ColMuxSelect signal value of 1 selects input port 1 of each column multiplexer 340, and each input port 1 of each column multiplexer 340 is coupled 342 to byte 1 of word 0, 1, 2 or 3. A “read” ColMuxSelect signal value of 2 selects input port 2 of each column multiplexer 340, and each input port 2 of each column multiplexer 340 is coupled 342 to byte 2 of word 0, 1, 2 or 3. And, a “read” ColMuxSelect signal value of 3 selects input port 3 of each column multiplexer 340, and each input port 3 of each column multiplexer 340 is coupled 342 to byte 3 of word 0, 1, 2 or 3.

Similarly, a “write” ColMuxSelect signal value of 0 selects output port 0 of each column multiplexer 350, and, as illustrated in FIG. 3C, each output port 0 of each column multiplexer 350 is coupled 352 to byte 0 of word 0, 1, 2 or 3. A “write” ColMuxSelect signal value of 1 selects output port 1 of each column multiplexer 350, and each output port 1 of each column multiplexer 350 is coupled 352 to byte 1 of word 0, 1, 2 or 3. A “write” ColMuxSelect signal value of 2 selects output port 2 of each column multiplexer 350, and each output port 2 of each column multiplexer 350 is coupled 352 to byte 2 of word 0, 1, 2 or 3. And, a “write” ColMuxSelect signal value of 3 selects output port 3 of each column multiplexer 350, and each output port 3 of each column multiplexer 350 is coupled 352 to byte 3 of word 0, 1, 2 or 3.

With respect to the systolic aspect of output stationary MAC array 228, the delay registers (i.e., flip flop blocks ff₁, ff₂ and ff₃) cost power and circuit area proportional to the size of the array. The cost of these delays is about N²−N flops for a square array of dimension N. Embodiments of the present disclosure advantageously eliminate the delay registers by changing the way data is read from, or written to, the memory without adding complexity and area to SRAM memories.

In the embodiment depicted in FIGS. 4A, 4B and 4C, the elements of each quadrant of converted input data matrix 214 are read from memory and provided to MAC array 228 in the proper sequence, as depicted in FIG. 2D. Because each quadrant of converted input data matrix 214 is stored in a single row or word line 310, the last element of each quadrant is read before the elements of the next quadrant of converted input data matrix 214 may be accessed.

In the embodiment depicted in FIGS. 5A, 5B and 5C, the elements of each quadrant of converted input data matrix 214 are read from memory and provided to MAC array 228 in the proper sequence, as depicted in FIG. 2D. Because adjacent quadrants of converted input data matrix 214 are stored in a single row or word line 310 in different memory banks, elements of both quadrants may be read during a single access.

In the embodiment depicted in FIGS. 6A, 6B, 6C, 6D and 6E, the elements of each quadrant of converted input data matrix 214 are written to memory in the proper sequence, as depicted in FIG. 2D. Because adjacent quadrants of converted input data matrix 214 are stored in a single row or word line 310 in different memory banks, elements of both quadrants may be written during a single access, and subsequently read during a single access.

FIG. 4A depicts a block diagram 400 of a memory for an ANN accelerator, in accordance with an embodiment of the present disclosure.

Block diagram 400 depicts a portion of a memory, such as, for example, a conventional, 32-bit static random-access memory (SRAM). Similar to the memory depicted in FIG. 3A, the size of a word is 32 bits or 4 bytes. Four rows or word lines 310 are depicted for illustration purposes, i.e., word line 0, word line 1, word line 2 and word line 3. Each word line has four, 32-bit words 320, i.e., word 0, word 1, word 2 and word 3, and each 32-bit word has 4 bytes 330, i.e., b0, b1, b2 and b3.

As noted above, a single access to a conventional 32-bit memory may only read (or write) a single word from (or to) a single row. A WordLineSelect signal identifies which row or word line 310 is to be accessed, such as, for example, word line 0, word line 1, word line 2, word line 3, etc. A column multiplexer 440 is coupled to the memory cells that store each word 320 of each word line 310, i.e., ColMux 0 is coupled to word 0 of word lines 0, 1, 2 and 3, ColMux 1 is coupled to word 1 of word lines 0, 1, 2 and 3, ColMux 2 is coupled to word 2 of word lines 0, 1, 2 and 3, and ColMux 3 is coupled to word 3 of word lines 0, 1, 2 and 3.

In this embodiment, column multiplexers 440 are associated with a memory read operation. Each “read” column multiplexer 440 has four 8-bit input ports and one 8-bit output port, and each input port is coupled to a different byte 330 of word 320, i.e., b0, b1, b2 or b3. A “read” ColMuxSelect signal identifies which input port of each column multiplexer 440 is to be selected, i.e., a value of 0 selects input port 0, a value of 1 selects input port 1, a value of 2 selects input port 2, and a value of 3 selects input port 3. The output port of each column multiplexer 440 outputs the value of the byte coupled to the selected input port, and the byte values are then formed into the word to be read, i.e., ColMux 0 provides the first byte, ColMux 1 provides the second byte, ColMux 2 provides the third byte, and ColMux 3 provides the fourth byte.

In this embodiment, each input port of each column multiplexer 440 is coupled to a different byte of the associated word as follows. For ColMux 0, input port 0 is coupled to b0 of word 0 of word lines 0, 1, 2 and 3, input port 1 is coupled to b1 of word 0 of word lines 0, 1, 2 and 3, input port 2 is coupled to b2 of word 0 of word lines 0, 1, 2 and 3, and input port 3 is coupled to b3 of word 0 of word lines 0, 1, 2 and 3. For ColMux 1, input port 0 is coupled to b3 of word 1 of word lines 0, 1, 2 and 3, input port 1 is coupled to b0 of word 1 of word lines 0, 1, 2 and 3, input port 2 is coupled to b1 of word 1 of word lines 0, 1, 2 and 3, and input port 3 is coupled to b2 of word 1 of word lines 0, 1, 2 and 3. For ColMux 2, input port 0 is coupled to b2 of word 2 of word lines 0, 1, 2 and 3, input port 1 is coupled to b3 of word 2 of word lines 0, 1, 2 and 3, input port 2 is coupled to b0 of word 2 of word lines 0, 1, 2 and 3, and input port 3 is coupled to b1 of word 2 of word lines 0, 1, 2 and 3. And, for ColMux 3, input port 0 is coupled to b1 of word 3 of word lines 0, 1, 2 and 3, input port 1 is coupled to b2 of word 3 of word lines 0, 1, 2 and 3, input port 2 is coupled to b3 of word 3 of word lines 0, 1, 2 and 3, and input port 3 is coupled to b0 of word 3 of word lines 0, 1, 2 and 3.

In one example, in response to a WordLineSelect signal of having a value of 0 and a ColMuxSelect signal of having a value of 0, word line 0 is selected, input port 0 of each column multiplexer 440 is selected, four bytes are read from the memory and a word is formed from b0 of word 0 of word line 0 (i.e., the output of ColMux 0), b3 of word 1 of word line 0 (i.e., the output of ColMux 1), b2 of word 2 of word line 0 (i.e., the output of ColMux 2), and b1 of word 3 of word line 0 (i.e., the output of ColMux 3).

As depicted in FIG. 4A, for illustration purposes, converted input data matrix 214 has been stored in word lines 0, 1, 2 and 3 of the memory in column-order. Each word line 310 stores one quadrant of converted input data matrix 214, i.e., word line 0 stores quadrant a_(q1), word line 1 stores quadrant a_(q2), word line 2 stores quadrant a_(q3), and word line 3 stores quadrant a_(q4). While converted input data matrix 214 has been depicted, converted weight matrix 212 may be similarly be stored in a different word line of the memory in row-order (rather than column-order), and similarly accessed for each quadrant of converted input data matrix 214.

In this embodiment, additional column multiplexers 350 (depicted in FIG. 4C; not depicted in FIG. 4A for clarity) may be associated with a memory write operation, as described above. Other memory characteristics, such as, for example, different sized words (e.g., 64 bits, etc.), different numbers of column multiplexers (e.g., 2, 8, 16, etc.), etc., are also contemplated.

FIG. 4B depicts a data flow diagram 402 for a sequence of read operations from a memory of an ANN accelerator, in accordance with an embodiment of the present disclosure.

In this embodiment, seven processing cycles are needed to read all of the elements from each quadrant of converted input data matrix 214, and 28 read cycles are needed to read all four quadrants of converted input data matrix 214. During each read cycle, four elements from one quadrant of converted input data matrix 214 are read from a single word line of the memory. The 28 read cycle sequence simply repeats for the next converted input data matrix 214 to be processed.

In the first read cycle for each quadrant of converted input data matrix 214 (i.e., read cycles 1, 8, 15 and 22), word 0 is read and provided to MAC array 228, while words 1, 2 and 3 are read but not provided to MAC array 228. In the second read cycle for each quadrant of converted input data matrix 214 (i.e., 2, 9, 16 and 23), words 0 and 1 are read and provided to MAC array 228, while words 2 and 3 are read but not provided to MAC array 228. In the third read cycle for each quadrant of converted input data matrix 214 (i.e., 3, 10, 17 and 24), words 0, 1 and 2 are read and provided to MAC array 228, while word 3 is read but not provided to MAC array 228. In the fourth read cycle for each quadrant of converted input data matrix 214 (i.e., 4, 11, 18 and 25), words 0, 1, 2 and 3 are read and provided to MAC array 228.

In the fifth read cycle for each quadrant of converted input data matrix 214 (i.e., 5, 12, 19 and 26), words 1, 2 and 3 are read and provided to MAC array 228, while word 0 is read but not provided to MAC array 228. In the sixth read cycle for each quadrant of converted input data matrix 214 (i.e., 6, 13, 20 and 27), words 1 and 2 are read and provided to MAC array 228, while words 0 and 1 are read but not provided to MAC array 228. In the seventh read cycle for each quadrant of converted input data matrix 214 (i.e., 7, 14, 21 and 28), word 3 is read and provided to MAC array 228, while words 0, 1 and 2 are read but not provided to MAC array 228.

Generally, a sense amplifier is coupled to each column multiplexer 440. For read cycles that include one or more elements that are not provided to MAC array 228, the sense amplifier for the respective column multiplexer 440 may be disabled to prevent reading the memory cells in which these element are stored. For example, a SenseAmplifierSelect signal may be provided to each sense amplifier to enable or disable the sense amplifier, which advantageously saves power. The SenseAmplifierSelect signal may be generated locally or globally. In this embodiment, 28 elements are read for each quadrant of converted input data matrix 214, however, 12 of those elements are not provided to MAC array 228. The power reduction provided by disabling the sense amplifiers for those elements that are not provided to MAC array 228 is equal to (12/28)*36%, or about 15%.

In another embodiment, all of four elements may be provided to MAC array 228 during each read cycle without effecting the accuracy of the dot product calculations because each MAC unit outputs the result of the dot product calculation at the end of the processing cycle in which the dot product calculation is complete, and each MAC unit is reset at the beginning of the processing cycle in which the first element of the next dot product calculation for the next quadrant of converted input data matrix 214 is received.

With respect to converted convolution operation 211 described above, for quadrant a_(q1) of converted input data matrix 214, MAC unit m₁ begins the calculation of the first converted output data element o¹ ₄ at the start of processing cycle 1 and completes the calculation at the end of processing cycle 4, while MAC unit m₁₆ begins the calculation of the last converted output data element o⁴ ₄ at the start of processing cycle 7 and completes the calculation at the end of processing cycle 10. For quadrant a_(q2) of converted input data matrix 214, MAC unit m₁ begins the calculation of the first converted output data element o¹ ₄ at the start of processing cycle 8 and completes the calculation at the end of processing cycle 11, while MAC unit m₁₆ begins the calculation of the last converted output data element o⁴ ₄ at the start of processing cycle 14 and completes the calculation at the end of processing cycle 17.

For quadrant a_(q3) of converted input data matrix 214, MAC unit m₁ begins the calculation of the first converted output data element o¹ ₄ at the start of processing cycle 15 and completes the calculation at the end of processing cycle 18, while MAC unit m₁₆ begins the calculation of the last converted output data element o⁴ ₄ at the start of processing cycle 21 and completes the calculation at the end of processing cycle 24. And, for quadrant a_(q4) of converted input data matrix 214, MAC unit m₁ begins the calculation of the first converted output data element o¹ ₄ at the start of processing cycle 22 and completes the calculation at the end of processing cycle 25, while MAC unit m₁₆ begins the calculation of the last converted output data element o⁴ ₄ at the start of processing cycle 28 and completes the calculation at the end of processing cycle 31.

Compared to data flow diagram 302, data flow diagram 402 requires an additional 9 processing cycles to complete the dot product calculations for converted input data matrix 214, i.e., 31 processing cycles as compared to 22 processing cycles.

For read cycles 1 to 7, the WordLineSelect signal is set to a value of 0 to access word line 0.

The initial four elements of quadrant a_(q1) of converted input data matrix 214, i.e., elements a₁, a₈, a₈ and a₅, are read at the beginning of processing cycle 1, which corresponds to read cycle 1 depicted in FIG. 4B. For read cycle 1, the ColMuxSelect signal is set to a value of 0, and the following bytes are selected and read from the memory by column multiplexers 440: b0 of word 0 of word line 0 (i.e., a₁) by ColMux 0, b3 of word 1 of word line 0 (i.e., a₈) by ColMux 1, b2 of word 2 of word line 0 (i.e., a₈) by ColMux 2, and b1 of word 3 of word line 0 (i.e., a₅) by ColMux 3.

The next four elements of quadrant a_(q1) of converted input data matrix 214, i.e., elements a₂, a₂, a₉ and a₉, are read at the beginning of processing cycle 2, which corresponds to read cycle 2 depicted in FIG. 4B. For read cycle 2, the ColMuxSelect signal is set to a value of 1, and the following bytes are selected and read from the memory by column multiplexers 440: b1 of word 0 of word line 0 (i.e., a₂) by ColMux 0, b0 of word 1 of word line 0 (i.e., a₂) by ColMux 1, b3 of word 2 of word line 0 (i.e., a₉) by ColMux 2, and b2 of word 3 of word line 0 (i.e., a₉) by ColMux 3.

The next four elements of quadrant a_(q1) of converted input data matrix 214, i.e., elements a₆, a₃, a₃ and a₁₀, are read at the beginning of processing cycle 3, which corresponds to read cycle 3 depicted in FIG. 4B. For read cycle 3, the ColMuxSelect signal is set to a value of 2, and the following bytes are selected and read from the memory by column multiplexers 440: b2 of word 0 of word line 0 (i.e., a₆) by ColMux 0, b1 of word 1 of word line 0 (i.e., a₃) by ColMux 1, b0 of word 2 of word line 0 (i.e., a₃) by ColMux 2, and b3 of word 3 of word line 0 (i.e., a₁₀) by ColMux 3.

The next four elements of quadrant a_(q1) of converted input data matrix 214, i.e., elements a₇, a₇, a₄ and a₄, are read at the beginning of processing cycle 4, which corresponds to read cycle 4 depicted in FIG. 4B. For read cycle 4, the ColMuxSelect signal is set to a value of 3, and the following bytes are selected and read from the memory by column multiplexers 340: b3 of word 0 of word line 0 (i.e., a₇) by ColMux 0, b2 of word 1 of word line 0 (i.e., a₇) by ColMux 1, b1 of word 2 of word line 0 (i.e., a₄) by ColMux 2, and b0 of word 3 of word line 0 (i.e., a₄) by ColMux 3.

The next four elements of quadrant a_(q1) of converted input data matrix 214, i.e., elements a₁, a₈, a₉ and a₅, are read at the beginning of processing cycle 5, which corresponds to read cycle 5 depicted in FIG. 4B. For read cycle 5, the ColMuxSelect signal is set to a value of 0, and the following bytes are selected and read from the memory by column multiplexers 440: b0 of word 0 of word line 0 (i.e., a₁) by ColMux 0, b3 of word 1 of word line 0 (i.e., a₈) by ColMux 1, b2 of word 2 of word line 0 (i.e., a₈) by ColMux 2, and b1 of word 3 of word line 0 (i.e., a₅) by ColMux 3. Read cycle 5 reads the same elements of quadrant a_(q1) of converted input data matrix 214 as read cycle 1 because the WordLineSelect signal and the ColMuxSelect signal are set to the same values.

The next four elements of quadrant a_(q1) of converted input data matrix 214, i.e., elements a₂, a₂, a₉ and a₉, are read at the beginning of processing cycle 6, which corresponds to read cycle 6 depicted in FIG. 4B. For read cycle 6, the ColMuxSelect signal is set to a value of 1, and the following bytes are selected and read from the memory by column multiplexers 440: b1 of word 0 of word line 0 (i.e., a₂) by ColMux 0, b0 of word 1 of word line 0 (i.e., a₂) by ColMux 1, b3 of word 2 of word line 0 (i.e., a₉) by ColMux 2, and b2 of word 3 of word line 0 (i.e., a₉) by ColMux 3. Read cycle 6 reads the same elements of quadrant a_(q1) of converted input data matrix 214 as read cycle 2 because the WordLineSelect signal and the ColMuxSelect signal are set to the same values.

The last four elements of quadrant a_(q1) of converted input data matrix 214, i.e., elements a₆, a₃, a₃ and a₁₀, are read at the beginning of processing cycle 7, which corresponds to read cycle 7 depicted in FIG. 4B. For read cycle 7, the ColMuxSelect signal is set to a value of 2, and the following bytes are selected and read from the memory by column multiplexers 440: b2 of word 0 of word line 0 (i.e., a₆) by ColMux 0, b1 of word 1 of word line 0 (i.e., a₃) by ColMux 1, b0 of word 2 of word line 0 (i.e., a₃) by ColMux 2, and b3 of word 3 of word line 0 (i.e., a₁₀) by ColMux 3. Read cycle 7 reads the same elements of quadrant a_(q1) of converted input data matrix 214 as read cycle 3 because the WordLineSelect signal and the ColMuxSelect signal are set to the same values.

For read cycles 8 to 14, the WordLineSelect signal is set to a value of 1 to access word line 1.

The initial four elements of quadrant a_(q2) of converted input data matrix 214, i.e., elements a₆, a₁₃, a₁₃ and a₁₀, are read at the beginning of processing cycle 8, which corresponds to read cycle 8 depicted in FIG. 4B. For read cycle 8, the ColMuxSelect signal is set to a value of 0, and the following bytes are selected and read from the memory by column multiplexers 440: b0 of word 0 of word line 1 (i.e., a₆) by ColMux 0, b3 of word 1 of word line 1 (i.e., a₁₃) by ColMux 1, b2 of word 2 of word line 1 (i.e., a₁₃) by ColMux 2, and b1 of word 3 of word line 1 (i.e., a₁₀) by ColMux 3.

The next four elements row of quadrant a_(q2) of converted input data matrix 214, i.e., elements a₇, a₇, a₁₄ and a₁₄, are read at the beginning of processing cycle 9, which corresponds to read cycle 9 depicted in FIG. 4B. For read cycle 9, the ColMuxSelect signal is set to a value of 1, and the following bytes are selected and read from the memory by column multiplexers 440: b1 of word 0 of word line 1 (i.e., a₇) by ColMux 0, b0 of word 1 of word line 1 (i.e., a₇) by ColMux 1, b3 of word 2 of word line 1 (i.e., a₁₄) by ColMux 2, and b2 of word 3 of word line 1 (i.e., a₁₄) by ColMux 3.

The next four elements of quadrant a_(q2) of converted input data matrix 214, i.e., elements a₁₁, a₈, a₉ and a₁₅, are read at the beginning of processing cycle 10, which corresponds to read cycle 10 depicted in FIG. 4B. For read cycle 10, the ColMuxSelect signal is set to a value of 2, and the following bytes are selected and read from the memory by column multiplexers 440: b2 of word 0 of word line 1 (i.e., a₁₁) by ColMux 0, b1 of word 1 of word line 1 (i.e., as) by ColMux 1, b0 of word 2 of word line 1 (i.e., as) by ColMux 2, and b3 of word 3 of word line 1 (i.e., a₁₅) by ColMux 3.

The next four elements of quadrant a_(q2) of converted input data matrix 214, i.e., elements a₁₂, a₁₂, a₉ and a₉, are read at the beginning of processing cycle 11, which corresponds to read cycle 11 depicted in FIG. 4B. For read cycle 11, the ColMuxSelect signal is set to a value of 3, and the following bytes are selected and read from the memory by column multiplexers 440: b3 of word 0 of word line 1 (i.e., a₁₂) by ColMux 0, b2 of word 1 of word line 1 (i.e., a₁₂) by ColMux 1, b1 of word 2 of word line 1 (i.e., a₉) by ColMux 2, and b0 of word 3 of word line 1 (i.e., a₉) by ColMux 3.

The next four elements of quadrant a_(q2) of converted input data matrix 214, i.e., elements a₆, a₁₃, a₁₃ and a₁₀, are read at the beginning of processing cycle 12, which corresponds to read cycle 12 depicted in FIG. 4B. For read cycle 12, the ColMuxSelect signal is set to a value of 0, and the following bytes are selected and read from the memory by column multiplexers 440: b0 of word 0 of word line 1 (i.e., a₆) by ColMux 0, b3 of word 1 of word line 1 (i.e., a₁₃) by ColMux 1, b2 of word 2 of word line 1 (i.e., a₁₃) by ColMux 2, and b1 of word 3 of word line 1 (i.e., a₁₀) by ColMux 3. Read cycle 12 reads the same elements of quadrant a_(q2) of converted input data matrix 214 as read cycle 8 because the WordLineSelect signal and the ColMuxSelect signal are set to the same values.

The next four elements of quadrant a_(q2) of converted input data matrix 214, i.e., elements a₇, a₇, a₁₄ and a₁₄, are read at the beginning of processing cycle 13, which corresponds to read cycle 13 depicted in FIG. 4B. For read cycle 13, the ColMuxSelect signal is set to a value of 1, and the following bytes are selected and read from the memory by column multiplexers 440: b1 of word 0 of word line 1 (i.e., a₇) by ColMux 0, b0 of word 1 of word line 1 (i.e., a₇) by ColMux 1, b3 of word 2 of word line 1 (i.e., a₁₄) by ColMux 2, and b2 of word 3 of word line 1 (i.e., a₁₄) by ColMux 3. Read cycle 13 reads the same elements of quadrant a_(q2) of converted input data matrix 214 as read cycle 9 because the WordLineSelect signal and the ColMuxSelect signal are set to the same values.

The last four elements of quadrant a_(q2) of converted input data matrix 214, i.e., elements a₁₁, a₈, a₈ and a₁₅, are read at the beginning of processing cycle 14, which corresponds to read cycle 14 depicted in FIG. 4B. For read cycle 14, the ColMuxSelect signal is set to a value of 2, and the following bytes are selected and read from the memory by column multiplexers 440: b2 of word 0 of word line 1 (i.e., a₁₁) by ColMux 0, b1 of word 1 of word line 1 (i.e., as) by ColMux 1, b0 of word 2 of word line 1 (i.e., as) by ColMux 2, and b3 of word 3 of word line 1 (i.e., a₁₅) by ColMux 3. Read cycle 14 reads the same elements of quadrant a_(q2) of converted input data matrix 214 as read cycle 10 because the WordLineSelect signal and the ColMuxSelect signal are set to the same values.

For read cycles 15 to 21, the WordLineSelect signal is set to a value of 2 to access word line 2.

The initial four elements of quadrant a_(q3) of converted input data matrix 214, i.e., elements a₁₁, a₁₈, a₁₈ and a₁₅, are read at the beginning of processing cycle 15, which corresponds to read cycle 15 depicted in FIG. 4B. For read cycle 15, the ColMuxSelect signal is set to a value of 0, and the following bytes are selected and read from the memory by column multiplexers 440: b0 of word 0 of word line 2 (i.e., a₁₁) by ColMux 0, b3 of word 1 of word line 2 (i.e., a₁₈) by ColMux 1, b2 of word 2 of word line 2 (i.e., a₁₈) by ColMux 2, and b1 of word 3 of word line 2 (i.e., a₁₅) by ColMux 3.

The next four elements row of quadrant a_(q3) of converted input data matrix 214, i.e., elements a₁₂, a₁₂, a₁₉ and a₁₉, are read at the beginning of processing cycle 16, which corresponds to read cycle 16 depicted in FIG. 4B. For read cycle 16, the ColMuxSelect signal is set to a value of 1, and the following bytes are selected and read from the memory by column multiplexers 440: b1 of word 0 of word line 2 (i.e., a₁₂) by ColMux 0, b0 of word 1 of word line 2 (i.e., a₁₂) by ColMux 1, b3 of word 2 of word line 2 (i.e., a₁₉) by ColMux 2, and b2 of word 3 of word line 2 (i.e., a₁₉) by ColMux 3.

The next four elements of quadrant a_(q3) of converted input data matrix 214, i.e., elements a₁₆, a₁₃, a₁₃ and a₂₀, are read at the beginning of processing cycle 17, which corresponds to read cycle 17 depicted in FIG. 4B. For read cycle 17, the ColMuxSelect signal is set to a value of 2, and the following bytes are selected and read from the memory by column multiplexers 440: b2 of word 0 of word line 2 (i.e., a₁₆) by ColMux 0, b1 of word 1 of word line 2 (i.e., a₁₃) by ColMux 1, b0 of word 2 of word line 2 (i.e., a₁₃) by ColMux 2, and b3 of word 3 of word line 2 (i.e., a₂₀) by ColMux 3.

The next four elements of quadrant a_(q3) of converted input data matrix 214, i.e., elements a₁₇, a₁₇, a₁₄ and a₁₄, are read at the beginning of processing cycle 18, which corresponds to read cycle 18 depicted in FIG. 4B. For read cycle 18, the ColMuxSelect signal is set to a value of 3, and the following bytes are selected and read from the memory by column multiplexers 440: b3 of word 0 of word line 2 (i.e., a₁₇) by ColMux 0, b2 of word 1 of word line 2 (i.e., a₁₇) by ColMux 1, b1 of word 2 of word line 2 (i.e., a₁₄) by ColMux 2, and b0 of word 3 of word line 2 (i.e., a₁₄) by ColMux 3.

The next four elements of quadrant a_(q3) of converted input data matrix 214, i.e., elements a₁₁, a₁₈, a₁₈ and a₁₅, are read at the beginning of processing cycle 19, which corresponds to read cycle 19 depicted in FIG. 4B. For read cycle 19, the ColMuxSelect signal is set to a value of 0, and the following bytes are selected and read from the memory by column multiplexers 440: b0 of word 0 of word line 1 (i.e., a₁₁) by ColMux 0, b3 of word 1 of word line 1 (i.e., a₁₈) by ColMux 1, b2 of word 2 of word line 1 (i.e., a₁₈) by ColMux 2, and b1 of word 3 of word line 1 (i.e., a₁₅) by ColMux 3. Read cycle 19 reads the same elements of quadrant a_(q3) of converted input data matrix 214 as read cycle 15 because the WordLineSelect signal and the ColMuxSelect signal are set to the same values.

The next four elements of quadrant a_(q3) of converted input data matrix 214, i.e., elements a₁₂, a₁₂, a₁₉ and a₁₉, are read at the beginning of processing cycle 20, which corresponds to read cycle 20 depicted in FIG. 4B. For read cycle 20, the ColMuxSelect signal is set to a value of 1, and the following bytes are selected and read from the memory by column multiplexers 440: b1 of word 0 of word line 2 (i.e., a₁₂) by ColMux 0, b0 of word 1 of word line 2 (i.e., a₁₂) by ColMux 1, b3 of word 2 of word line 2 (i.e., a₁₉) by ColMux 2, and b2 of word 3 of word line 2 (i.e., a₁₉) by ColMux 3. Read cycle 20 reads the same elements of quadrant a_(q2) of converted input data matrix 214 as read cycle 16 because the WordLineSelect signal and the ColMuxSelect signal are set to the same values.

The last four elements of quadrant a_(q3) of converted input data matrix 214, i.e., elements a₁₆, a₁₃, a₁₃ and a₂₀, are read at the beginning of processing cycle 21, which corresponds to read cycle 21 depicted in FIG. 4B. For read cycle 21, the ColMuxSelect signal is set to a value of 2, and the following bytes are selected and read from the memory by column multiplexers 440: b2 of word 0 of word line 2 (i.e., a₁₆) by ColMux 0, b1 of word 1 of word line 2 (i.e., a₁₃) by ColMux 1, b0 of word 2 of word line 2 (i.e., a₁₃) by ColMux 2, and b3 of word 3 of word line 2 (i.e., a₂₀) by ColMux 3. Read cycle 21 reads the same elements of quadrant a_(q2) of converted input data matrix 214 as read cycle 17 because the WordLineSelect signal and the ColMuxSelect signal are set to the same values.

For read cycles 22 to 28, the WordLineSelect signal is set to a value of 3 to access word line 3.

The initial four elements of quadrant a_(q4) of converted input data matrix 214, i.e., elements a₁₆, a₂₃, a₂₃ and a₂₀, are read at the beginning of processing cycle 22, which corresponds to read cycle 22 depicted in FIG. 4B. For read cycle 22, the ColMuxSelect signal is set to a value of 0, and the following bytes are selected and read from the memory by column multiplexers 440: b0 of word 0 of word line 3 (i.e., a₁₆) by ColMux 0, b3 of word 1 of word line 3 (i.e., a₂₃) by ColMux 1, b2 of word 2 of word line 3 (i.e., a₂₃) by ColMux 2, and b1 of word 3 of word line 3 (i.e., a₂₀) by ColMux 3.

The next four elements row of quadrant a_(q4) of converted input data matrix 214, i.e., elements a₁₇, a₁₇, a₂₄ and a₂₄, are read at the beginning of processing cycle 23, which corresponds to read cycle 23 depicted in FIG. 4B. For read cycle 23, the ColMuxSelect signal is set to a value of 1, and the following bytes are selected and read from the memory by column multiplexers 440: b1 of word 0 of word line 3 (i.e., a₁₇) by ColMux 0, b0 of word 1 of word line 3 (i.e., a₁₇) by ColMux 1, b3 of word 2 of word line 3 (i.e., a₂₄) by ColMux 2, and b2 of word 3 of word line 3 (i.e., a₂₄) by ColMux 3.

The next four elements of quadrant a_(q4) of converted input data matrix 214, i.e., elements a₂₁, a₁₈, a₁₈ and a₂₅, are read at the beginning of processing cycle 24, which corresponds to read cycle 24 depicted in FIG. 4B. For read cycle 24, the ColMuxSelect signal is set to a value of 2, and the following bytes are selected and read from the memory by column multiplexers 440: b2 of word 0 of word line 3 (i.e., a₂₁) by ColMux 0, b1 of word 1 of word line 3 (i.e., a₁₈) by ColMux 1, b0 of word 2 of word line 3 (i.e., a₁₈) by ColMux 2, and b3 of word 3 of word line 3 (i.e., a₂₅) by ColMux 3.

The next four elements of quadrant a_(q4) of converted input data matrix 214, i.e., elements a₂₂, a₂₂, a₁₉ and a₁₉, are read at the beginning of processing cycle 25, which corresponds to read cycle 25 depicted in FIG. 4B. For read cycle 25, the ColMuxSelect signal is set to a value of 3, and the following bytes are selected and read from the memory by column multiplexers 440: b3 of word 0 of word line 3 (i.e., a₂₂) by ColMux 0, b2 of word 1 of word line 3 (i.e., a₂₂) by ColMux 1, b1 of word 2 of word line 3 (i.e., a₁₉) by ColMux 2, and b0 of word 3 of word line 3 (i.e., a₁₉) by ColMux 3.

The next four elements of quadrant a_(q4) of converted input data matrix 214, i.e., elements a₁₆, a₂₃, a₂₃ and a₂₀, are read at the beginning of processing cycle 26, which corresponds to read cycle 26 depicted in FIG. 4B. For read cycle 26, the ColMuxSelect signal is set to a value of 0, and the following bytes are selected and read from the memory by column multiplexers 440: b0 of word 0 of word line 3 (i.e., a₁₆) by ColMux 0, b3 of word 1 of word line 3 (i.e., a₂₃) by ColMux 1, b2 of word 2 of word line 3 (i.e., a₂₃) by ColMux 2, and b1 of word 3 of word line 3 (i.e., a₂₀) by ColMux 3. Read cycle 26 reads the same elements of quadrant a_(q3) of converted input data matrix 214 as read cycle 22 because the WordLineSelect signal and the ColMuxSelect signal are set to the same values.

The next four elements of quadrant a_(q4) of converted input data matrix 214, i.e., elements a₁₇, a₁₇, a₂₄ and a₂₄, are read at the beginning of processing cycle 27, which corresponds to read cycle 27 depicted in FIG. 4B. For read cycle 27, the ColMuxSelect signal is set to a value of 1, and the following bytes are selected and read from the memory by column multiplexers 440: b1 of word 0 of word line 3 (i.e., a₁₇) by ColMux 0, b0 of word 1 of word line 3 (i.e., a₁₇) by ColMux 1, b3 of word 2 of word line 3 (i.e., a₂₄) by ColMux 2, and b2 of word 3 of word line 3 (i.e., a₂₄) by ColMux 3. Read cycle 27 reads the same elements of quadrant a_(q2) of converted input data matrix 214 as read cycle 23 because the WordLineSelect signal and the ColMuxSelect signal are set to the same values.

The last four elements of quadrant a_(q4) of converted input data matrix 214, i.e., elements a₂₁, a₁₈, a₁₈ and a₂₅, are read at the beginning of processing cycle 28, which corresponds to read cycle 28 depicted in FIG. 4B. For read cycle 28, the ColMuxSelect signal is set to a value of 2, and the following bytes are selected and read from the memory by column multiplexers 440: b2 of word 0 of word line 3 (i.e., a₂₁) by ColMux 0, b1 of word 1 of word line 3 (i.e., a₁₈) by ColMux 1, b0 of word 2 of word line 3 (i.e., a₁₈) by ColMux 2, and b3 of word 3 of word line 3 (i.e., a₂₅) by ColMux 3. Read cycle 28 reads the same elements of quadrant a_(q2) of converted input data matrix 214 as read cycle 24 because the WordLineSelect signal and the ColMuxSelect signal are set to the same values.

FIG. 4C depicts a word selector or multiplexer mapping diagram 404 for a memory for an ANN accelerator, in accordance with an embodiment of the present disclosure.

As described above, the memory may include four column multiplexers 440 associated with read operations, and four column multiplexers 450 associated with write operations. Multiplexer mapping diagram 404 illustrates the mapping between the “read” ColMuxSelect signal values (i.e., 0, 1, 2 and 3) and the bytes 330 of each word 320, as well as the mapping between the “write” ColMuxSelect signal values (i.e., 0, 1, 2 and 3) and the bytes 330 of each word 320.

A “read” ColMuxSelect signal value of 0 selects input port 0 of column multiplexers 440. Input port 0 of the first column multiplexer 440 (i.e., ColMux 0) is coupled 442 to byte 0 of word 0, input port 0 of the second column multiplexer 440 (i.e., ColMux 1) is coupled 442 to byte 3 of word 1, input port 0 of the third column multiplexer 440 (i.e., ColMux 2) is coupled 442 to byte 2 of word 2, and input port 0 of the fourth column multiplexer 440 (i.e., ColMux 3) is coupled 442 to byte 1 of word 3.

A “read” ColMuxSelect signal value of 1 selects input port 1 of each column multiplexer 440. Input port 1 of the first column multiplexer 440 (i.e., ColMux 0) is coupled 442 to byte 1 of word 0, input port 1 of the second column multiplexer 440 (i.e., ColMux 1) is coupled 442 to byte 0 of word 1, input port 1 of the third column multiplexer 440 (i.e., ColMux 2) is coupled 442 to byte 3 of word 2, and input port 1 of the fourth column multiplexer 440 (i.e., ColMux 3) is coupled 442 to byte 2 of word 3.

A “read” ColMuxSelect signal value of 2 selects input port 2 of each column multiplexer 440. Input port 2 of the first column multiplexer 440 (i.e., ColMux 0) is coupled 442 to byte 2 of word 0, input port 2 of the second column multiplexer 440 (i.e., ColMux 1) is coupled 442 to byte 1 of word 1, input port 2 of the third column multiplexer 440 (i.e., ColMux 2) is coupled 442 to byte 0 of word 2, and input port 2 of the fourth column multiplexer 440 (i.e., ColMux 3) is coupled 442 to byte 3 of word 3.

A “read” ColMuxSelect signal value of 3 selects input port 3 of each column multiplexer 440. Input port 3 of the first column multiplexer 440 (i.e., ColMux 0) is coupled 442 to byte 3 of word 0, input port 3 of the second column multiplexer 440 (i.e., ColMux 1) is coupled 442 to byte 2 of word 1, input port 3 of the third column multiplexer 440 (i.e., ColMux 2) is coupled 442 to byte 1 of word 2, and input port 3 of the fourth column multiplexer 440 (i.e., ColMux 3) is coupled 442 to byte 0 of word 3.

A “write” ColMuxSelect signal value of 0 selects output port 0 of each column multiplexer 450, and, as illustrated in FIG. 4C, each output port 0 of each column multiplexer 450 is coupled 452 to byte 0 of word 0, 1, 2 or 3. A “write” ColMuxSelect signal value of 1 selects output port 1 of each column multiplexer 450, and each output port 1 of each column multiplexer 450 is coupled 452 to byte 1 of word 0, 1, 2 or 3. A “write” ColMuxSelect signal value of 2 selects output port 2 of each column multiplexer 450, and each output port 2 of each column multiplexer 450 is coupled 452 to byte 2 of word 0, 1, 2 or 3. And, a “write” ColMuxSelect signal value of 3 selects output port 3 of each column multiplexer 450, and each output port 3 of each column multiplexer 450 is coupled 352 to byte 3 of word 0, 1, 2 or 3.

Generally, for a memory with two banks, the number of bytes per word must be less than or equal to the number of bytes per row plus 1. Memories with larger word sizes require additional memory banks and larger systolic MAC arrays. For example, a 64-bit memory uses 8 bytes per word, three banks and an 8×8 MAC array, and most read cycles access three banks at the same time.

FIG. 5A depicts a block diagram 500 of a memory for an ANN accelerator, in accordance with an embodiment of the present disclosure.

Block diagram 500 depicts a portion of a multi-bank memory, such as, for example, a conventional, 32-bit static random-access memory (SRAM). Similar to the memory depicted in FIG. 4A, the size of a word is 32 bits or 4 bytes. Banks 510 and 511 are depicted for illustration purposes. Bank 510 has at least two rows or word lines 410, i.e., word line 0, word line 1, etc., while bank 511 has at least two rows or word lines 411, i.e., word line 0, word line 1, etc. Each word line has four, 32-bit words 320, i.e., word 0, word 1, word 2 and word 3, and each 32-bit word has 4 bytes 330, i.e., b0, b1, b2 and b3.

A single access to a conventional 32-bit memory bank may only read (or write) a single word from (or to) a single row of that bank.

For bank 510, a first WordLineSelect signal identifies which row or word line 410 is to be accessed, such as, for example, word line 0, word line 1, etc. A column multiplexer 440 is coupled to the memory cells that store each word 320 of each word line 410, i.e., ColMux 0 is coupled to word 0 of word lines 0, 1, 2 and 3, ColMux 1 is coupled to word 1 of word lines 0, 1, 2 and 3, ColMux 2 is coupled to word 2 of word lines 0, 1, 2 and 3, and ColMux 3 is coupled to word 3 of word lines 0, 1, 2 and 3.

Similarly, for bank 511, a second WordLineSelect signal identifies which row or word line 411 is to be accessed, such as, for example, word line 0, word line 1, etc. A column multiplexer 441 is coupled to the memory cells that store each word 320 of each word line 411, i.e., ColMux 0 is coupled to word 0 of word lines 0, 1, 2 and 3, ColMux 1 is coupled to word 1 of word lines 0, 1, 2 and 3, ColMux 2 is coupled to word 2 of word lines 0, 1, 2 and 3, and ColMux 3 is coupled to word 3 of word lines 0, 1, 2 and 3.

In this embodiment, column multiplexers 440, 441 are associated with a memory read operation. Each “read” column multiplexer 440, 441 has four 8-bit input ports and one 8-bit output port, and each input port is coupled to a different byte 330 of word 320, i.e., b0, b1, b2 or b3. A “read” ColMuxSelect signal identifies which input port of each column multiplexer 440, 441 is to be selected, i.e., a value of 0 selects input port 0, a value of 1 selects input port 1, a value of 2 selects input port 2, and a value of 3 selects input port 3. The output port of each column multiplexer 440, 441 outputs the value of the byte coupled to the selected input port, and the byte values are then formed into the word to be read, i.e., ColMux 0 provides the first byte, ColMux 1 provides the second byte, ColMux 2 provides the third byte, and ColMux 3 provides the fourth byte.

In this embodiment, each input port of each column multiplexer 440, 441 is coupled to a different byte of the associated word as follows. For ColMux 0 in banks 510 and 511, input port 0 is coupled to b0 of word 0 of word lines 0, 1, etc., input port 1 is coupled to b1 of word 0 of word lines 0, 1, etc., input port 2 is coupled to b2 of word 0 of word lines 0, 1, etc., and input port 3 is coupled to b3 of word 0 of word lines 0, 1, etc. For ColMux 1 in banks 510 and 511, input port 0 is coupled to b3 of word 1 of word lines 0, 1, etc., input port 1 is coupled to b0 of word 1 of word lines 0, 1, etc., input port 2 is coupled to b1 of word 1 of word lines 0, 1, etc., and input port 3 is coupled to b2 of word 1 of word lines 0, 1, etc. For ColMux 2 in banks 510 and 511, input port 0 is coupled to b2 of word 2 of word lines 0, 1, etc., input port 1 is coupled to b3 of word 2 of word lines 0, 1, etc., input port 2 is coupled to b0 of word 2 of word lines 0, 1, etc., and input port 3 is coupled to b1 of word 2 of word lines 0, 1, etc. And, for ColMux 3 in banks 510 and 511, input port 0 is coupled to b1 of word 3 of word lines 0, 1, etc., input port 1 is coupled to b2 of word 3 of word lines 0, 1, etc., input port 2 is coupled to b3 of word 3 of word lines 0, 1, etc., and input port 3 is coupled to b0 of word 3 of word lines 0, 1, etc.

Read bank multiplexers 444, i.e., RMux 0, RMux 1, RMux 2 and RMux 3, are coupled to column multiplexers 440 of bank 510 and column multiplexers 441 of bank 511. Each read bank multiplexer 444 includes two 8-bit input ports and one 8-bit output port. The input ports of RMux 0 are coupled to ColMux 0 of bank 510 and ColMux 0 of bank 511, the input ports of RMux 1 are coupled to ColMux 1 of bank 510 and ColMux 1 of bank 511, the input ports of RMux 2 are coupled to ColMux 2 of bank 510 and ColMux 2 of bank 511, and the input ports of RMux 3 are coupled to ColMux 3 of bank 510 and ColMux 3 of bank 511.

A ReadBankMuxSelect signal identifies which column multiplexer 440, 441 is to be selected for each byte to be read. In one embodiment, the ReadBankMuxSelect signal includes 4 bits, each bit corresponding to a different read bank multiplexer 444. The most significant bit (msb) corresponds to RMux 0, the next bit corresponds to RMux 1, the next bit corresponds to RMux 2, and the least significant bit (Isb) corresponds to RMux 3. A value of 0 for a particular bit selects the respective column multiplexer 440 of bank 510, while the value of 1 for a particular bit selects the respective column multiplexer 441 of bank 511.

More particularly, a ReadBankMuxSelect signal having a binary value of 0000 (0 digital) selects the outputs from ColMuxs 0, 1, 2 and 3 of bank 510. A ReadBankMuxSelect signal having a binary value of 1000 (8 digital) selects the outputs from ColMuxs 1, 2 and 3 of bank 510 and the output from ColMux 0 of bank 511. A ReadBankMuxSelect signal having a binary value of 1100 (12 digital) selects the outputs from ColMuxs 2 and 3 of bank 510 and the outputs from ColMuxs 0 and 1 of bank 511. A ReadBankMuxSelect signal having a binary value of 1110 (14 digital) selects the output from ColMux 3 from bank 510 and the outputs from ColMuxs 0, 1 and 2 of bank 511. A ReadBankMuxSelect signal having a binary value of 1111 (15 digital) selects the outputs from ColMuxs 0, 1, 2 and 3 of bank 511.

The output port of each read bank multiplexer 444 provides the output of the selected column multiplexer 440, 441, and the byte values are then formed into the word to be read, i.e., RMux 0 provides the first byte, RMux 1 provides the second byte, RMux 2 provides the third byte, and RMux 3 provides the fourth byte.

As depicted in FIG. 5A, for illustration purposes, converted input data matrix 214 has been stored in word lines 410, 411 of banks 510, 511 of the memory in column-order. Each word line 410, 411 stores one quadrant of converted input data matrix 214, i.e., word line 0 of bank 510 stores quadrant a_(q1), word line 1 of bank 510 stores quadrant a_(q3), word line 0 of bank 511 stores quadrant a_(q2), and word line 1 of bank 511 stores quadrant a_(q4). Converted weight matrix 212 may be similarly be stored in two different banks of the memory in row-order (rather than column-order).

In this embodiment, additional column multiplexers 450, 451 (depicted in FIG. 5C; not depicted in FIG. 5A for clarity) may be associated with a memory write operation, as described above. Other memory characteristics, such as, for example, different sized words (e.g., 64 bits, etc.), different numbers of column multiplexers (e.g., 2, 8, 16, etc.), etc., are also contemplated.

FIG. 5B depicts a data flow diagram 502 for a sequence of read operations from a memory of an ANN accelerator, in accordance with an embodiment of the present disclosure.

In this embodiment, seven processing cycles are needed to read all of the elements from each quadrant of converted input data matrix 214, and 19 processing cycles are needed to read all four quadrants of converted input data matrix 214. During each read cycle, four elements from one quadrant or a combination of elements from two quadrants of converted input data matrix 214 are read from banks 510, 511 of the memory.

With respect to converted convolution operation 211 described above, for quadrant a_(q1) of converted input data matrix 214, MAC unit m₁ begins the calculation of the first converted output data element o¹ ₄ at the start of processing cycle 1 and completes the calculation at the end of processing cycle 4, while MAC unit m₁₆ begins the calculation of the last converted output data element o⁴ ₄ at the start of processing cycle 7 and completes the calculation at the end of processing cycle 10. For quadrant a_(q2) of converted input data matrix 214, MAC unit m₁ begins the calculation of the first converted output data element o¹ ₄ at the start of processing cycle 5 and completes the calculation at the end of processing cycle 8, while MAC unit m₁₆ begins the calculation of the last converted output data element o⁴ ₄ at the start of processing cycle 11 and completes the calculation at the end of processing cycle 14.

For quadrant a_(q3) of converted input data matrix 214, MAC unit m₁ begins the calculation of the first converted output data element o¹ ₄ at the start of processing cycle 9 and completes the calculation at the end of processing cycle 12, while MAC unit m₁₆ begins the calculation of the last converted output data element o⁴ ₄ at the start of processing cycle 15 and completes the calculation at the end of processing cycle 18. And, for quadrant a_(q4) of converted input data matrix 214, MAC unit m₁ begins the calculation of the first converted output data element o¹ ₄ at the start of processing cycle 13 and completes the calculation at the end of processing cycle 16, while MAC unit m₁₆ begins the calculation of the last converted output data element o⁴ ₄ at the start of processing cycle 19 and completes the calculation at the end of processing cycle 22.

Compared to data flow diagram 302, data flow diagram 502 advantageously requires the same number of processing cycles to complete the dot product calculations for converted input data matrix 214, i.e., 22 processing cycles, without the need for delay registers or ff₁ blocks which cost power and circuit area proportional to the size of the array.

For read cycles 1 to 4, the WordLineSelect signal for bank 510 is set to a value of 0 to access word line 0, and the WordLineSelect signal for bank 511 is set to a value of 0 to access word line 0.

The initial four elements of quadrant a_(q1) of converted input data matrix 214, i.e., elements a₁, a₈, a₉ and a₅, are read at the beginning of processing cycle 1, which corresponds to read cycle 1 depicted in FIG. 5B. As discussed above, elements a₈, a₈ and a₅ may be read and not provided to MAC array 228, or the sense amplifiers associated with the column multiplexers for these elements may be disabled to prevent reading the memory cells in which these elements are stored. For read cycle 1, the ReadBankMuxSelect signal is set to a binary value of 0000 (0 digital), the ColMuxSelect signals for column multiplexers 440, 441 are set to a value of 0, and the following bytes are selected and read from the memory by column multiplexers 440 and/or column multiplexers 441: b0 of word 0 of word line 0 (i.e., a₁) by ColMux 0 of bank 510, b3 of word 1 of word line 0 (i.e., as) by ColMux 1 of bank 510, b2 of word 2 of word line 0 (i.e., as) by ColMux 2 of bank 510, and b1 of word 3 of word line 0 (i.e., a₅) by ColMux 3 of bank 510.

The next four elements of quadrant a_(q1) of converted input data matrix 214, i.e., elements a₂, a₂, a₉ and a₉, are read at the beginning of processing cycle 2, which corresponds to read cycle 2 depicted in FIG. 5B. As discussed above, elements a₉ and a₉ may be read and not provided to MAC array 228, or the sense amplifiers associated with the column multiplexers for these elements may be disabled to prevent reading the memory cells in which these elements are stored. For read cycle 2, the ReadBankMuxSelect signal is set to a binary value of 0000 (0 digital), the ColMuxSelect signals for column multiplexers 440, 441 are set to a value of 1, and the following bytes are selected and read from the memory by column multiplexers 440 and/or column multiplexers 441: b1 of word 0 of word line 0 (i.e., a₂) by ColMux 0 of bank 510, b0 of word 1 of word line 0 (i.e., a₂) by ColMux 1 of bank 510, b3 of word 2 of word line 0 (i.e., a₉) by ColMux 2 of bank 510, and b2 of word 3 of word line 0 (i.e., a₉) by ColMux 3 of bank 510.

The next four elements of quadrant a_(q1) of converted input data matrix 214, i.e., elements a₆, a₃, a₃ and a₁₀, are read at the beginning of processing cycle 3, which corresponds to read cycle 3 depicted in FIG. 5B. As discussed above, element a₁₀ may be read and not provided to MAC array 228, or the sense amplifiers associated with the column multiplexers for this element may be disabled to prevent reading the memory cells in which this element are stored. For read cycle 3, the ReadBankMuxSelect signal is set to a binary value of 0000 (0 digital), the ColMuxSelect signals for column multiplexers 440, 441 are set to a value of 2, and the following bytes are selected and read from the memory by column multiplexers 440 and/or column multiplexers 441: b2 of word 0 of word line 0 (i.e., a₆) by ColMux 0 of bank 510, b1 of word 1 of word line 0 (i.e., a₃) by ColMux 1 of bank 510, b0 of word 2 of word line 0 (i.e., a₃) by ColMux 2 of bank 510, and b3 of word 3 of word line 0 (i.e., a₁₀) by ColMux 3 of bank 510.

The next four elements of quadrant a_(q1) of converted input data matrix 214, i.e., elements a₇, a₇, a₄ and a₄, are read at the beginning of processing cycle 4, which corresponds to read cycle 4 depicted in FIG. 5B. For read cycle 4, the ReadBankMuxSelect signal is set to a binary value of 0000 (0 digital), the ColMuxSelect signals for column multiplexers 440, 441 are set to a value of 3, and the following bytes are selected and read from the memory by column multiplexers 440 and/or column multiplexers 441: b3 of word 0 of word line 0 (i.e., a₇) by ColMux 0 of bank 510, b2 of word 1 of word line 0 (i.e., a₇) by ColMux 1 of bank 510, b1 of word 2 of word line 0 (i.e., a₄) by ColMux 2 of bank 510, and b0 of word 3 of word line 0 (i.e., a₄) by ColMux 3 of bank 510.

For read cycles 5 to 8, the WordLineSelect signal for bank 510 is set to a value of 0 to access word line 0, and the WordLineSelect signal for bank 511 is set to a value of 0 to access word line 0 (i.e., the same values as read cycles 1 to 4).

The first element of quadrant a_(q2) of converted input data matrix 214, i.e., element a₆, and the next three elements of quadrant a_(q1) of converted input data matrix 214, i.e., elements a₈, a₈ and a₅, are read at the beginning of processing cycle 5, which corresponds to read cycle 5 depicted in FIG. 5B. For read cycle 5, the ReadBankMuxSelect signal is set to a binary value of 1000 (8 digital), the ColMuxSelect signals for column multiplexers 440, 441 are set to a value of 0, and the following bytes are selected and read from the memory by column multiplexers 440 and/or column multiplexers 441: b0 of word 0 of word line 0 (i.e., a₆) by ColMux 0 of bank 511, b3 of word 1 of word line 0 (i.e., as) by ColMux 1 of bank 510, b2 of word 2 of word line 0 (i.e., as) by ColMux 2 of bank 510, and b1 of word 3 of word line 0 (i.e., a₅) by ColMux 3 of bank 510.

The next two elements of quadrant a_(q2) of converted input data matrix 214, i.e., elements a₇ and a₇, and the next two elements of quadrant a_(q1) of converted input data matrix 214, i.e., elements a₉ and a₉, are read at the beginning of processing cycle 6, which corresponds to read cycle 6 depicted in FIG. 5B. For read cycle 6, the ReadBankMuxSelect signal is set to a binary value of 1100 (12 digital), the ColMuxSelect signals for column multiplexers 440, 441 are set to a value of 1, and the following bytes are selected and read from the memory by column multiplexers 440 and/or column multiplexers 441: b1 of word 0 of word line 0 (i.e., a₇) by ColMux 0 of bank 511, b0 of word 1 of word line 0 (i.e., a₇) by ColMux 1 of bank 511, b3 of word 2 of word line 0 (i.e., a₉) by ColMux 2 of bank 510, and b2 of word 3 of word line 0 (i.e., a₉) by ColMux 3 of bank 510.

The next three elements of quadrant a_(q2) of converted input data matrix 214, i.e., elements a₁₁, a₈ and a₈, and the last element of quadrant a_(q1) of converted input data matrix 214, i.e., element a₁₀, are read at the beginning of processing cycle 7, which corresponds to read cycle 7 depicted in FIG. 5B. For read cycle 7, the ReadBankMuxSelect signal is set to a binary value of 1110 (14 digital), the ColMuxSelect signals for column multiplexers 440, 441 are set to a value of 2, and the following bytes are selected and read from the memory by column multiplexers 440 and/or column multiplexers 441: b2 of word 0 of word line 0 (i.e., a₁₁) by ColMux 0 of bank 511, b1 of word 1 of word line 0 (i.e., as) by ColMux 1 of bank 511, b0 of word 2 of word line 0 (i.e., as) by ColMux 2 of bank 511, and b3 of word 3 of word line 0 (i.e., a₁₀) by ColMux 3 of bank 510.

The next four elements of quadrant a_(q2) of converted input data matrix 214, i.e., elements a₁₂, a₁₂, a₉ and a₉, are read at the beginning of processing cycle 8, which corresponds to read cycle 8 depicted in FIG. 5B. For read cycle 8, the ReadBankMuxSelect signal is set to a binary value of 1111 (15 digital), the ColMuxSelect signals for column multiplexers 440, 441 are set to a value of 3, and the following bytes are selected and read from the memory by column multiplexers 440 and/or column multiplexers 441: b3 of word 0 of word line 0 (i.e., a₁₂) by ColMux 0 of bank 511, b2 of word 1 of word line 0 (i.e., a₁₂) by ColMux 1 of bank 511, b1 of word 2 of word line 0 (i.e., a₉) by ColMux 2 of bank 511, and b0 of word 3 of word line 0 (i.e., a₉) by ColMux 3 of bank 511.

For read cycles 9 to 12, the WordLineSelect signal for bank 510 is set to a value of 1 to access word line 1, and the WordLineSelect signal for bank 511 is set to a value of 0 to access word line 0.

The first element of quadrant a_(q3) of converted input data matrix 214, i.e., element a₁₁, and the next three elements of quadrant a_(q2) of converted input data matrix 214, i.e., elements a₁₃, a₁₃ and a₁₀, are read at the beginning of processing cycle 9, which corresponds to read cycle 9 depicted in FIG. 5B. For read cycle 9, the ReadBankMuxSelect signal is set to a binary value of 0111 (7 digital), the ColMuxSelect signals for column multiplexers 440, 441 are set to a value of 0, and the following bytes are selected and read from the memory by column multiplexers 440 and/or column multiplexers 441: b0 of word 0 of word line 1 (i.e., a₁₁) by ColMux 0 of bank 510, b3 of word 1 of word line 0 (i.e., a₁₃) by ColMux 1 of bank 511, b2 of word 2 of word line 0 (i.e., a₁₃) by ColMux 2 of bank 511, and b1 of word 3 of word line 0 (i.e., a₁₀) by ColMux 3 of bank 511.

The next two elements of quadrant a_(q3) of converted input data matrix 214, i.e., elements a₁₂ and a₁₂, and the next two elements of quadrant a_(q2) of converted input data matrix 214, i.e., elements a₁₄ and a₁₄, are read at the beginning of processing cycle 10, which corresponds to read cycle 10 depicted in FIG. 5B. For read cycle 10, the ReadBankMuxSelect signal is set to a binary value of 0011 (3 digital), the ColMuxSelect signals for column multiplexers 440, 441 are set to a value of 1, and the following bytes are selected and read from the memory by column multiplexers 440 and/or column multiplexers 441: b1 of word 0 of word line 1 (i.e., a₁₂) by ColMux 0 of bank 510, b0 of word 1 of word line 1 (i.e., a₁₂) by ColMux 1 of bank 510, b3 of word 2 of word line 0 (i.e., a₁₄) by ColMux 2 of bank 511, and b2 of word 3 of word line 0 (i.e., a₁₄) by ColMux 3 of bank 511.

The next three elements of quadrant a_(q3) of converted input data matrix 214, i.e., elements a₁₆, a₁₃ and a₁₃, and the last element of quadrant a_(q2) of converted input data matrix 214, i.e., element a₁₅, are read at the beginning of processing cycle 11, which corresponds to read cycle 11 depicted in FIG. 5B. For read cycle 11, the ReadBankMuxSelect signal is set to a binary value of 0001 (1 digital), the ColMuxSelect signals for column multiplexers 440, 441 are set to a value of 2, and the following bytes are selected and read from the memory by column multiplexers 440 and/or column multiplexers 441: b2 of word 0 of word line 1 (i.e., a₁₆) by ColMux 0 of bank 510, b1 of word 1 of word line 1 (i.e., a₁₃) by ColMux 1 of bank 510, b0 of word 2 of word line 1 (i.e., a₁₃) by ColMux 2 of bank 510, and b3 of word 3 of word line 0 (i.e., a₁₅) by ColMux 3 of bank 511.

The next four elements of quadrant a_(q3) of converted input data matrix 214, i.e., elements a₁₇, a₁₇, a₁₄ and a₁₄, are read at the beginning of processing cycle 12, which corresponds to read cycle 12 depicted in FIG. 5B. For read cycle 12, the ReadBankMuxSelect signal is set to a binary value of 0000 (0 digital), the ColMuxSelect signals for column multiplexers 440, 441 are set to a value of 3, and the following bytes are selected and read from the memory by column multiplexers 440 and/or column multiplexers 441: b3 of word 0 of word line 1 (i.e., a₁₇) by ColMux 0 of bank 510, b2 of word 1 of word line 1 (i.e., a₁₇) by ColMux 1 of bank 510, b1 of word 2 of word line 1 (i.e., a₁₄) by ColMux 2 of bank 510, and b0 of word 3 of word line 1 (i.e., a₁₄) by ColMux 3 of bank 510.

For read cycles 13 to 16, the WordLineSelect signal for bank 510 is set to a value of 1 to access word line 1, and the WordLineSelect signal for bank 511 is set to a value of 1 to access word line 1.

The first element of quadrant a_(q4) of converted input data matrix 214, i.e., element a₁₆, and the next three elements of quadrant a_(q3) of converted input data matrix 214, i.e., elements a₁₈, a₁₈ and a₁₅, are read at the beginning of processing cycle 13, which corresponds to read cycle 13 depicted in FIG. 5B. For read cycle 13, the ReadBankMuxSelect signal is set to a binary value of 1000 (8 digital), the ColMuxSelect signals for column multiplexers 440, 441 are set to a value of 0, and the following bytes are selected and read from the memory by column multiplexers 440 and/or column multiplexers 441: b0 of word 0 of word line 1 (i.e., a₁₆) by ColMux 0 of bank 511, b3 of word 1 of word line 1 (i.e., a₁₈) by ColMux 1 of bank 510, b2 of word 2 of word line 1 (i.e., a₁₈) by ColMux 2 of bank 510, and b1 of word 3 of word line 1 (i.e., a₁₅) by ColMux 3 of bank 510.

The next two elements of quadrant a_(q4) of converted input data matrix 214, i.e., elements a₁₇ and a₁₇, and the next two elements of quadrant a_(q3) of converted input data matrix 214, i.e., elements a₁₉ and a₁₉, are read at the beginning of processing cycle 14, which corresponds to read cycle 14 depicted in FIG. 5B. For read cycle 14, the ReadBankMuxSelect signal is set to a binary value of 1100 (12 digital), the ColMuxSelect signals for column multiplexers 440, 441 are set to a value of 1, and the following bytes are selected and read from the memory by column multiplexers 440 and/or column multiplexers 441: b1 of word 0 of word line 1 (i.e., a₁₇) by ColMux 0 of bank 511, b0 of word 1 of word line 1 (i.e., a₁₇) by ColMux 1 of bank 511, b3 of word 2 of word line 1 (i.e., a₁₉) by ColMux 2 of bank 510, and b2 of word 3 of word line 1 (i.e., a₁₉) by ColMux 3 of bank 510.

The next three elements of quadrant a_(q4) of converted input data matrix 214, i.e., elements a₂₁, a₁₈ and a₁₈, and the next element of quadrant a_(q3) of converted input data matrix 214, i.e., element a₂₀, are read at the beginning of processing cycle 15, which corresponds to read cycle 15 depicted in FIG. 5B. For read cycle 15, the ReadBankMuxSelect signal is set to a binary value of 1110 (14 digital), the ColMuxSelect signals for column multiplexers 440, 441 are set to a value of 2, and the following bytes are selected and read from the memory by column multiplexers 440 and/or column multiplexers 441: b2 of word 0 of word line 1 (i.e., a₂₁) by ColMux 0 of bank 511, b1 of word 1 of word line 1 (i.e., a₁₈) by ColMux 1 of bank 511, b0 of word 2 of word line 1 (i.e., a₁₈) by ColMux 2 of bank 511, and b3 of word 3 of word line 1 (i.e., a₂₀) by ColMux 3 of bank 510.

The next four elements of quadrant a_(q4) of converted input data matrix 214, i.e., elements a₂₂, a₂₂, a₁₉ and a₁₉, are read at the beginning of processing cycle 16, which corresponds to read cycle 16 depicted in FIG. 5B. For read cycle 16, the ReadBankMuxSelect signal is set to a binary value of 1111 (15 digital), the ColMuxSelect signals for column multiplexers 440, 441 are set to a value of 3, and the following bytes are selected and read from the memory by column multiplexers 440 and/or column multiplexers 441: b3 of word 0 of word line 1 (i.e., a₂₂) by ColMux 0 of bank 511, b2 of word 1 of word line 1 (i.e., a₂₂) by ColMux 1 of bank 511, b1 of word 2 of word line 1 (i.e., a₁₉) by ColMux 2 of bank 511, and b0 of word 3 of word line 1 (i.e., a₁₉) by ColMux 3 of bank 511.

For read cycles 17 to 19, the WordLineSelect signal for bank 510 is set to a value of 2 to access word line 2 (not depicted in FIG. 5A), and the WordLineSelect signal for bank 511 is set to a value of 1 to access word line 1.

The first element of quadrant b_(q1) (not depicted) of the next converted input data matrix 214 (not depicted), i.e., element b₁, and the next three elements of quadrant a_(q4) of converted input data matrix 214, i.e., elements a₂₃, a₂₃ and a₂₀, are read at the beginning of processing cycle 17, which corresponds to read cycle 17 depicted in FIG. 5B. For read cycle 17, the ReadBankMuxSelect signal is set to a binary value of 0111 (7 digital), the ColMuxSelect signals for column multiplexers 440, 441 are set to a value of 0, and the following bytes are selected and read from the memory by column multiplexers 440 and/or column multiplexers 441: b0 of word 0 of word line 2 (i.e., b₁) by ColMux 0 of bank 510, b3 of word 1 of word line 1 (i.e., a₂₃) by ColMux 1 of bank 511, b2 of word 2 of word line 1 (i.e., a₂₃) by ColMux 2 of bank 511, and b1 of word 3 of word line 1 (i.e., a₂₀) by ColMux 3 of bank 511.

The next two elements of quadrant b_(q1) of the next converted input data matrix 214, i.e., elements b2 and b2, and the next two elements of quadrant a_(q4) of converted input data matrix 214, i.e., elements a₂₄ and a₂₄, are read at the beginning of processing cycle 18, which corresponds to read cycle 18 depicted in FIG. 5B. For read cycle 18, the ReadBankMuxSelect signal is set to a binary value of 0011 (3 digital), the ColMuxSelect signals for column multiplexers 440, 441 are set to a value of 1, and the following bytes are selected and read from the memory by column multiplexers 440 and/or column multiplexers 441: b1 of word 0 of word line 2 (i.e., b2) by ColMux 0 of bank 510, b0 of word 1 of word line 2 (i.e., b2) by ColMux 1 of bank 510, b3 of word 2 of word line 1 (i.e., a₂₄) by ColMux 2 of bank 511, and b2 of word 3 of word line 1 (i.e., a₂₄) by ColMux 3 of bank 511.

The next three elements of quadrant b_(q1) of the next converted input data matrix 214, i.e., elements b6, b3 and b3, and the last element of quadrant a_(q4) of converted input data matrix 214, i.e., element a₂₅, are read at the beginning of processing cycle 19, which corresponds to read cycle 19 depicted in FIG. 5B. For read cycle 19, the ReadBankMuxSelect signal is set to a binary value of 0001 (1 digital), the ColMuxSelect signals for column multiplexers 440, 441 are set to a value of 2, and the following bytes are selected and read from the memory by column multiplexers 440 and/or column multiplexers 441: b2 of word 0 of word line 2 (i.e., b6) by ColMux 0 of bank 510, b1 of word 1 of word line 2 (i.e., b₃) by ColMux 1 of bank 510, b0 of word 2 of word line 2 (i.e., b₃) by ColMux 2 of bank 510, and b₃ of word 3 of word line 1 (i.e., a₂₅) by ColMux 3 of bank 511.

And so on.

FIG. 5C depicts a word selector or multiplexer mapping diagram 504 for a memory for an ANN accelerator, in accordance with an embodiment of the present disclosure.

As described above, bank 510 and 511 of the memory may include four column multiplexers 440 and 441 (respectively) associated with read operations, and four column multiplexers 450 and 451 (respectively) associated with write operations. Multiplexer mapping diagram 504 illustrates the mapping between the “read” ColMuxSelect signal values (i.e., 0, 1, 2 and 3) and the bytes 330 of each word 320, as well as the mapping between the “write” ColMuxSelect signal values (i.e., 0, 1, 2 and 3) and the bytes 330 of each word 320.

A “read” ColMuxSelect signal value of 0 selects input port 0 of column multiplexers 440, 441. Input port 0 of the first column multiplexer 440, 441 (i.e., ColMux 0) is coupled 442 to byte 0 of word 0, input port 0 of the second column multiplexer 440, 441 (i.e., ColMux 1) is coupled 442 to byte 3 of word 1, input port 0 of the third column multiplexer 440, 441 (i.e., ColMux 2) is coupled 442 to byte 2 of word 2, and input port 0 of the fourth column multiplexer 440, 441 (i.e., ColMux 3) is coupled 442 to byte 1 of word 3.

A “read” ColMuxSelect signal value of 1 selects input port 1 of each column multiplexer 440, 441. Input port 1 of the first column multiplexer 440, 441 (i.e., ColMux 0) is coupled 442 to byte 1 of word 0, input port 1 of the second column multiplexer 440, 441 (i.e., ColMux 1) is coupled 442 to byte 0 of word 1, input port 1 of the third column multiplexer 440, 441 (i.e., ColMux 2) is coupled 442 to byte 3 of word 2, and input port 1 of the fourth column multiplexer 440, 441 (i.e., ColMux 3) is coupled 442 to byte 2 of word 3.

A “read” ColMuxSelect signal value of 2 selects input port 2 of each column multiplexer 440, 441. Input port 2 of the first column multiplexer 440, 441 (i.e., ColMux 0) is coupled 442 to byte 2 of word 0, input port 2 of the second column multiplexer 440, 441 (i.e., ColMux 1) is coupled 442 to byte 1 of word 1, input port 2 of the third column multiplexer 440, 441 (i.e., ColMux 2) is coupled 442 to byte 0 of word 2, and input port 2 of the fourth column multiplexer 440, 441 (i.e., ColMux 3) is coupled 442 to byte 3 of word 3.

A “read” ColMuxSelect signal value of 3 selects input port 3 of each column multiplexer 440, 441. Input port 3 of the first column multiplexer 440, 441 (i.e., ColMux 0) is coupled 442 to byte 3 of word 0, input port 3 of the second column multiplexer 440, 441 (i.e., ColMux 1) is coupled 442 to byte 2 of word 1, input port 3 of the third column multiplexer 440, 441 (i.e., ColMux 2) is coupled 442 to byte 1 of word 2, and input port 3 of the fourth column multiplexer 440, 441 (i.e., ColMux 3) is coupled 442 to byte 0 of word 3.

A “write” ColMuxSelect signal value of 0 selects output port 0 of each column multiplexer 450, 451, and, as illustrated in FIG. 5C, each output port 0 of each column multiplexer 450, 451 is coupled 452 to byte 0 of word 0, 1, 2 or 3. A “write” ColMuxSelect signal value of 1 selects output port 1 of each column multiplexer 450, 451, and each output port 1 of each column multiplexer 450, 451 is coupled 452 to byte 1 of word 0, 1, 2 or 3. A “write” ColMuxSelect signal value of 2 selects output port 2 of each column multiplexer 450, 451, and each output port 2 of each column multiplexer 450, 451 is coupled 452 to byte 2 of word 0, 1, 2 or 3. And, a “write” ColMuxSelect signal value of 3 selects output port 3 of each column multiplexer 450, 451, and each output port 3 of each column multiplexer 450, 451 is coupled 452 to byte 3 of word 0, 1, 2 or 3.

FIG. 6A depicts a block diagram 600 of a memory for an ANN accelerator, in accordance with an embodiment of the present disclosure.

Block diagram 600 depicts a portion of a multi-bank memory, such as, for example, a conventional, 32-bit static random-access memory (SRAM). Similar to the memory depicted in FIG. 5A, the size of a word is 32 bits or 4 bytes. Banks 510 and 511 are depicted for illustration purposes. Bank 510 has at least two rows or word lines 410, i.e., word line 0, word line 1, etc., while bank 511 has at least two rows or word lines 411, i.e., word line 0, word line 1, etc. Each word line has four, 32-bit words 320, i.e., word 0, word 1, word 2 and word 3, and each 32-bit word has 4 bytes 330, i.e., b0, b1, b2 and b3.

A single access to a conventional 32-bit memory bank may only write (or read) a single word to (or from) a single row of that bank.

For bank 510, a first WordLineSelect signal identifies which row or word line 410 is to be accessed, such as, for example, word line 0, word line 1, etc. A column multiplexer 450 is coupled to the memory cells that store each word 320 of each word line 410, i.e., ColMux 0 is coupled to word 0 of word lines 0, 1, etc., ColMux 1 is coupled to word 1 of word lines 0, 1, etc., ColMux 2 is coupled to word 2 of word lines 0, 1, etc., and ColMux 3 is coupled to word 3 of word lines 0, 1, etc.

Similarly, for bank 511, a second WordLineSelect signal identifies which row or word line 411 is to be accessed, such as, for example, word line 0, word line 1, etc. A column multiplexer 451 is coupled to the memory cells that store each word 320 of each word line 411, i.e., ColMux 0 is coupled to word 0 of word lines 0, 1, etc., ColMux 1 is coupled to word 1 of word lines 0, 1, etc., ColMux 2 is coupled to word 2 of word lines 0, 1, etc., and ColMux 3 is coupled to word 3 of word lines 0, 1, etc.

In this embodiment, column multiplexers 450, 451 are associated with a memory write operation. Each “write” column multiplexer 450, 451 has four 8-bit output ports and one 8-bit input port, and each output port is coupled to a different byte 330 of word 320, i.e., b0, b1, b2 or b3. A “write” ColMuxSelect signal identifies which output port of each column multiplexer 450, 451 is to be selected, i.e., a value of 0 selects output port 0, a value of 1 selects output port 1, a value of 2 selects output port 2, and a value of 3 selects output port 3. The input port of each column multiplexer 450, 451 receives the value of the byte of the word to be written to the selected output port, ColMux 0 writes the first byte, ColMux 1 writes the second byte, ColMux 2 writes the third byte, and ColMux 3 writes the fourth byte.

In this embodiment, each output port of each column multiplexer 450, 451 is coupled to a different byte of the associated word as follows. For ColMux 0 in banks 510 and 511, input port 0 is coupled to b0 of word 0 of word lines 0, 1, etc., input port 1 is coupled to b1 of word 0 of word 0, 1, etc., input port 2 is coupled to b2 of word 0 of word lines 0, 1, etc., and input port 3 is coupled to b3 of word 0 of word lines 0, 1, etc. For ColMux 1 in banks 510 and 511, input port 0 is coupled to b1 of word 1 of word lines 0, 1, etc., input port 1 is coupled to b2 of word 1 of word lines 0, 1, etc., input port 2 is coupled to b3 of word 1 of word lines 0, 1, etc., and input port 3 is coupled to b0 of word 1 of word lines 0, 1, etc. For ColMux 2 in banks 510 and 511, input port 0 is coupled to b2 of word 2 of word lines 0, 1, etc., input port 1 is coupled to b3 of word 2 of word lines 0, 1, etc., input port 2 is coupled to b0 of word 2 of word lines 0, 1, etc., and input port 3 is coupled to b1 of word 2 of word lines 0, 1, etc. And, for ColMux 3 in banks 510 and 511, input port 0 is coupled to b3 of word 3 of word lines 0, 1, etc., input port 1 is coupled to b0 of word 3 of word lines 0, 1, etc., input port 2 is coupled to b1 of word 3 of word lines 0, 1, etc., and input port 3 is coupled to b2 of word 3 of word lines 0, 1, etc.

Write bank multiplexers 454, i.e., WMux 0, WMux 1, WMux 2 and WMux 3, are coupled to column multiplexers 450 of bank 510 and column multiplexers 451 of bank 511. Each write bank multiplexer 454 includes two 8-bit output ports and one 8-bit input port. The output ports of WMux 0 are coupled to ColMux 0 of bank 510 and ColMux 0 of bank 511, the output ports of WMux 1 are coupled to ColMux 1 of bank 510 and ColMux 1 of bank 511, the output ports of WMux 2 are coupled to ColMux 2 of bank 510 and ColMux 2 of bank 511, and the output ports of WMux 3 are coupled to ColMux 3 of bank 510 and ColMux 3 of bank 511.

A WriteBankMuxSelect signal identifies which column multiplexer 450, 451 is to be selected for each byte to be written. In one embodiment, the WriteBankMuxSelect signal includes 4 bits, each bit corresponding to a different write bank multiplexer 454. The most significant bit (msb) corresponds to WMux 0, the next bit corresponds to WMux 1, the next bit corresponds to WMux 2, and the least significant bit (Isb) corresponds to WMux 3. A value of 0 for a particular bit selects the respective column multiplexer 450 of bank 510, while the value of 1 for a particular bit selects the respective column multiplexer 451 of bank 511.

More particularly, a WriteBankMuxSelect signal having a binary value of 0000 (0 digital) selects the inputs of ColMuxs 0, 1, 2 and 3 of bank 510. A WriteBankMuxSelect signal having a binary value of 1000 (8 digital) selects the inputs of ColMuxs 1, 2 and 3 of bank 510 and the input of ColMux 0 of bank 511. A WriteBankMuxSelect signal having a binary value of 1100 (12 digital) selects the inputs of ColMuxs 2 and 3 of bank 510 and the inputs of ColMuxs 0 and 1 of bank 511. A WriteBankMuxSelect signal having a binary value of 1110 (14 digital) selects the input of ColMux 3 from bank 510 and the inputs of ColMuxs 0, 1 and 2 of bank 511. A WriteBankMuxSelect signal having a binary value of 1111 (15 digital) selects the inputs of ColMuxs 0, 1, 2 and 3 of bank 511.

The output port of each read bank multiplexer 454 provides one byte of the word to be written to the selected column multiplexer 450, 451, and the byte values are then written to the memory, i.e., WMux 0 provides the first byte, WMux 1 provides the second byte, WMux 2 provides the third byte, and WMux 3 provides the fourth byte.

As depicted in FIG. 6A, for illustration purposes, converted input data matrix 214 (except for several elements of quadrant a_(q4)) has been stored in word lines 410, 411 of banks 510, 511 of the memory. Each word line 410, 411 stores elements from one or two quadrants of converted input data matrix 214, i.e., word line 0 of bank 510 stores elements from quadrant a_(q1) and other data (i.e., elements x₁, x₂, x₃, y₂, y₃ and z₃), word line 1 of bank 510 stores elements from quadrants a_(q2) and a_(q3), word line 0 of bank 511 stores elements from quadrants a_(q1) and a_(q2), and word line 1 of bank 511 stores elements from quadrants a_(q3) and a_(q4). Converted weight matrix 212 may be similarly be stored in two different banks of the memory in row-order (rather than column-order).

In this embodiment, additional column multiplexers 440, 441 (depicted in FIGS. 6C and 6E; not depicted in FIG. 6A for clarity) may be associated with a memory read operation, as described below. Other memory characteristics, such as, for example, different sized words (e.g., 64 bits, etc.), different numbers of column multiplexers (e.g., 2, 8, 16, etc.), etc., are also contemplated.

FIG. 6B depicts a data flow diagram 602 for a sequence of write operations to a memory of an ANN accelerator, in accordance with an embodiment of the present disclosure.

In this embodiment, four processing cycles are needed to write all of the elements from each quadrant of converted input data matrix 214, and 16 processing cycles are needed to write all four quadrants of converted input data matrix 214. During each write cycle, four elements from one quadrant are written to banks 510, 511 of the memory.

For write cycles 1 to 4, the WordLineSelect signal for bank 510 is set to a value of 0 to access word line 0, and the WordLineSelect signal for bank 511 is set to a value of 0 to access word line 0.

The first row of quadrant a_(q1) of converted input data matrix 214, i.e., elements a₁, a₂, a₃ and a₄, is written during write cycle 1. For write cycle 1, the WriteBankMuxSelect signal is set to a binary value of 0000 (0 digital), the ColMuxSelect signals for column multiplexers 450, 451 are set to a value of 0, and the following bytes are written to the memory by column multiplexers 450 and/or column multiplexers 451: b0 of word 0 of word line 0 (i.e., a₁) by ColMux 0 of bank 510, b1 of word 1 of word line 0 (i.e., a₂) by ColMux 1 of bank 510, b2 of word 2 of word line 0 (i.e., a₃) by ColMux 2 of bank 510, and b₃ of word 3 of word line 0 (i.e., a₄) by ColMux 3 of bank 510.

The second row of quadrant a_(q1) of converted input data matrix 214, i.e., elements a₂, a₃, a₄ and a₅, is written during write cycle 2. For write cycle 2, the WriteBankMuxSelect signal is set to a binary value of 0001 (1 digital), the ColMuxSelect signals for column multiplexers 450, 451 are set to a value of 1, and the following bytes are written to the memory by column multiplexers 450 and/or column multiplexers 451: b1 of word 0 of word line 0 (i.e., a₂) by ColMux 0 of bank 510, b2 of word 1 of word line 0 (i.e., a₃) by ColMux 1 of bank 510, b₃ of word 2 of word line 0 (i.e., a₄) by ColMux 2 of bank 510, and b0 of word 3 of word line 0 (i.e., a₅) by ColMux 3 of bank 511.

The third row of quadrant a_(q1) of converted input data matrix 214, i.e., elements a₆, a₇, a₈ and a₉, is written during write cycle 3. For write cycle 3, the WriteBankMuxSelect signal is set to a binary value of 0011 (3 digital), the ColMuxSelect signals for column multiplexers 450, 451 are set to a value of 2 and the following bytes are written to the memory by column multiplexers 450 and/or column multiplexers 451: b2 of word 0 of word line 0 (i.e., a₆) by ColMux 0 of bank 510, b₃ of word 1 of word line 0 (i.e., a₇) by ColMux 1 of bank 510, b0 of word 2 of word line 0 (i.e., as) by ColMux 2 of bank 511, and b1 of word 3 of word line 0 (i.e., a₉) by ColMux 3 of bank 511.

The fourth row of quadrant a_(q1) of converted input data matrix 214, i.e., elements a₇, a₈, a₉ and a₁₀, is written during write cycle 4. For write cycle 4, the WriteBankMuxSelect signal is set to a binary value of 0111 (7 digital), the ColMuxSelect signals for column multiplexers 450, 451 are set to a value of 3 and the following bytes are written to the memory by column multiplexers 450 and/or column multiplexers 451: b₃ of word 0 of word line 0 (i.e., a₇) by ColMux 0 of bank 510, b0 of word 1 of word line 0 (i.e., a₈) by ColMux 1 of bank 511, b1 of word 2 of word line 0 (i.e., a₉) by ColMux 2 of bank 511, and b2 of word 3 of word line 0 (i.e., a₁₀) by ColMux 3 of bank 511.

For write cycles 5 to 8, the WordLineSelect signal for bank 510 is set to a value of 1 to access word line 1, and the WordLineSelect signal for bank 511 is set to a value of 0 to access word line 0.

The first row of quadrant a_(q2) of converted input data matrix 214, i.e., elements a₆, a₇, a₈ and a₉, is written during write cycle 5. For write cycle 5, the WriteBankMuxSelect signal is set to a binary value of 1111 (15 digital), the ColMuxSelect signals for column multiplexers 450, 451 are set to a value of 0, and the following bytes are written to the memory by column multiplexers 450 and/or column multiplexers 451: b0 of word 0 of word line 0 (i.e., a₆) by ColMux 0 of bank 511, b1 of word 1 of word line 0 (i.e., a₇) by ColMux 1 of bank 511, b2 of word 2 of word line 0 (i.e., as) by ColMux 2 of bank 511, and b₃ of word 3 of word line 0 (i.e., a₉) by ColMux 3 of bank 511.

The second row of quadrant a_(q2) of converted input data matrix 214, i.e., elements a₇, a₈, a₉ and a₁₀, is written during write cycle 6. For write cycle 6, the WriteBankMuxSelect signal is set to a binary value of 1110 (14 digital), the ColMuxSelect signals for column multiplexers 450, 451 are set to a value of 1, and the following bytes are written to the memory by column multiplexers 450 and/or column multiplexers 451: b1 of word 0 of word line 0 (i.e., a₇) by ColMux 0 of bank 511, b2 of word 1 of word line 0 (i.e., a₈) by ColMux 1 of bank 511, b₃ of word 2 of word line 0 (i.e., a₉) by ColMux 2 of bank 511, and b0 of word 3 of word line 1 (i.e., a₁₀) by ColMux 3 of bank 510.

The third row of quadrant a_(q2) of converted input data matrix 214, i.e., elements a₁₁, a₁₂, a₁₃ and a₁₄, is written during write cycle 7. For write cycle 7, the WriteBankMuxSelect signal is set to a binary value of 1100 (12 digital), the ColMuxSelect signals for column multiplexers 450, 451 are set to a value of 2 and the following bytes are written to the memory by column multiplexers 450 and/or column multiplexers 451: b2 of word 0 of word line 0 (i.e., a₁₁) by ColMux 0 of bank 511, b₃ of word 1 of word line 0 (i.e., a₁₂) by ColMux 1 of bank 511, b0 of word 2 of word line 1 (i.e., a₁₃) by ColMux 2 of bank 510, and b1 of word 3 of word line 1 (i.e., a₁₄) by ColMux 3 of bank 510.

The fourth row of quadrant a_(q2) of converted input data matrix 214, i.e., elements a₁₂, a₁₃, a₁₄ and a₁₅, is written during write cycle 8. For write cycle 8, the WriteBankMuxSelect signal is set to a binary value of 1000 (8 digital), the ColMuxSelect signals for column multiplexers 450, 451 are set to a value of 3 and the following bytes are written to the memory by column multiplexers 450 and/or column multiplexers 451: b₃ of word 0 of word line 0 (i.e., a₁₂) by ColMux 0 of bank 511, b0 of word 1 of word line 1 (i.e., a₁₃) by ColMux 1 of bank 510, b1 of word 2 of word line 1 (i.e., a₁₄) by ColMux 2 of bank 510, and b2 of word 3 of word line 1 (i.e., a₁₅) by ColMux 3 of bank 510.

For write cycles 9 to 12, the WordLineSelect signal for bank 510 is set to a value of 1 to access word line 1, and the WordLineSelect signal for bank 511 is set to a value of 1 to access word line 1.

The first row of quadrant a_(q3) of converted input data matrix 214, i.e., elements a₁₁, a₁₂, a₁₃ and a₁₄, is written during write cycle 9. For write cycle 9, the WriteBankMuxSelect signal is set to a binary value of 0000 (0 digital), the ColMuxSelect signals for column multiplexers 450, 451 are set to a value of 0, and the following bytes are written to the memory by column multiplexers 450 and/or column multiplexers 451: b0 of word 0 of word line 1 (i.e., a₁₁) by ColMux 0 of bank 510, b1 of word 1 of word line 1 (i.e., a₁₂) by ColMux 1 of bank 510, b2 of word 2 of word line 1 (i.e., a₁₃) by ColMux 2 of bank 510, and b₃ of word 3 of word line 1 (i.e., a₁₄) by ColMux 3 of bank 510.

The second row of quadrant a_(q3) of converted input data matrix 214, i.e., elements a₁₂, a₁₃, a₁₄ and a₁₅, is written during write cycle 10. For write cycle 10, the WriteBankMuxSelect signal is set to a binary value of 0001 (1 digital), the ColMuxSelect signals for column multiplexers 450, 451 are set to a value of 1, and the following bytes are written to the memory by column multiplexers 450 and/or column multiplexers 451: b1 of word 0 of word line 1 (i.e., a₁₂) by ColMux 0 of bank 510, b2 of word 1 of word line 1 (i.e., a₁₃) by ColMux 1 of bank 510, b₃ of word 2 of word line 1 (i.e., a₁₄) by ColMux 2 of bank 510, and b0 of word 3 of word line 1 (i.e., a₁₅) by ColMux 3 of bank 511.

The third row of quadrant a_(q3) of converted input data matrix 214, i.e., elements a₁₆, a₁₇, a₁₈ and a₁₉, is written during write cycle 11. For write cycle 11, the WriteBankMuxSelect signal is set to a binary value of 0011 (3 digital), the ColMuxSelect signals for column multiplexers 450, 451 are set to a value of 2 and the following bytes are written to the memory by column multiplexers 450 and/or column multiplexers 451: b2 of word 0 of word line 1 (i.e., a₁₆) by ColMux 0 of bank 510, b₃ of word 1 of word line 1 (i.e., a₁₇) by ColMux 1 of bank 510, b0 of word 2 of word line 1 (i.e., a₁₈) by ColMux 2 of bank 511, and b1 of word 3 of word line 1 (i.e., a₁₉) by ColMux 3 of bank 511.

The fourth row of quadrant a_(q3) of converted input data matrix 214, i.e., elements a₁₇, a₁₈, a₁₉ and a₂₀, is written during write cycle 12. For write cycle 12, the WriteBankMuxSelect signal is set to a binary value of 0111 (7 digital), the ColMuxSelect signals for column multiplexers 450, 451 are set to a value of 3 and the following bytes are written to the memory by column multiplexers 450 and/or column multiplexers 451: b₃ of word 0 of word line 1 (i.e., a₁₇) by ColMux 0 of bank 510, b0 of word 1 of word line 1 (i.e., a₁₈) by ColMux 1 of bank 511, b1 of word 2 of word line 1 (i.e., a₁₉) by ColMux 2 of bank 511, and b2 of word 3 of word line 1 (i.e., a₂₀) by ColMux 3 of bank 511.

For write cycles 13 to 16, the WordLineSelect signal for bank 510 is set to a value of 2 to access word line 2 (not depicted in FIG. 6A), and the WordLineSelect signal for bank 511 is set to a value of 1 to access word line 1.

The first row of quadrant a_(q4) of converted input data matrix 214, i.e., elements a₁₆, a₁₇, a₁₈ and a₁₉, is written during write cycle 13. For write cycle 13, the WriteBankMuxSelect signal is set to a binary value of 1111 (15 digital), the ColMuxSelect signals for column multiplexers 450, 451 are set to a value of 0, and the following bytes are written to the memory by column multiplexers 450 and/or column multiplexers 451: b0 of word 0 of word line 1 (i.e., a₁₆) by ColMux 0 of bank 511, b1 of word 1 of word line 1 (i.e., a₁₇) by ColMux 1 of bank 511, b2 of word 2 of word line 1 (i.e., a₁₈) by ColMux 2 of bank 511, and b₃ of word 3 of word line 1 (i.e., a₁₉) by ColMux 3 of bank 511.

The second row of quadrant a_(q4) of converted input data matrix 214, i.e., elements a₁₇, a₁₈, a₁₉ and a₂₀, is written during write cycle 14. For write cycle 14, the WriteBankMuxSelect signal is set to a binary value of 1110 (14 digital), the ColMuxSelect signals for column multiplexers 450, 451 are set to a value of 1, and the following bytes are written to the memory by column multiplexers 450 and/or column multiplexers 451: b1 of word 0 of word line 1 (i.e., a₁₇) by ColMux 0 of bank 511, b2 of word 1 of word line 1 (i.e., a₁₈) by ColMux 1 of bank 511, b₃ of word 2 of word line 1 (i.e., a₁₉) by ColMux 2 of bank 511, and b0 of word 3 of word line 2 (i.e., a₂₀) by ColMux 3 of bank 510.

The third row of quadrant a_(q4) of converted input data matrix 214, i.e., elements a₂₁, a₂₂, a₂₃ and a₂₄, is written during write cycle 15. For write cycle 15, the WriteBankMuxSelect signal is set to a binary value of 1100 (12 digital), the ColMuxSelect signals for column multiplexers 450, 451 are set to a value of 2 and the following bytes are written to the memory by column multiplexers 450 and/or column multiplexers 451: b2 of word 0 of word line 1 (i.e., a₂₁) by ColMux 0 of bank 511, b₃ of word 1 of word line 1 (i.e., a₂₂) by ColMux 1 of bank 511, b0 of word 2 of word line 2 (i.e., a₂₃) by ColMux 2 of bank 510, and b1 of word 3 of word line 2 (i.e., a₂₄) by ColMux 3 of bank 510.

The fourth row of quadrant a_(q4) of converted input data matrix 214, i.e., elements a₂₂, a₂₃, a₂₄ and a₂₅, is written during write cycle 16. For write cycle 16, the WriteBankMuxSelect signal is set to a binary value of 1000 (8 digital), the ColMuxSelect signals for column multiplexers 450, 451 are set to a value of 3 and the following bytes are written to the memory by column multiplexers 450 and/or column multiplexers 451: b₃ of word 0 of word line 1 (i.e., a₂₂) by ColMux 0 of bank 511, b0 of word 1 of word line 2 (i.e., a₂₃) by ColMux 1 of bank 510, b1 of word 2 of word line 2 (i.e., a₂₄) by ColMux 2 of bank 510, and b2 of word 3 of word line 2 (i.e., a₂₅) by ColMux 3 of bank 510.

And so on for the next converted input data matrix 214.

FIG. 6C depicts a block diagram 601 of a memory for an ANN accelerator, in accordance with an embodiment of the present disclosure.

Block diagram 601 generally depicts the memory bank depicted in block diagram 600. In this embodiment, column multiplexers 440, 441 are associated with a memory read operation. Each “read” column multiplexer 440, 441 has four 8-bit input ports and one 8-bit output port, and each input port is coupled to a different byte 330 of word 320, i.e., b0, b1, b2 or b3. A “read” ColMuxSelect signal identifies which input port of each column multiplexer 440, 441 is to be selected, i.e., a value of 0 selects input port 0, a value of 1 selects input port 1, a value of 2 selects input port 2, and a value of 3 selects input port 3. The output port of each column multiplexer 440, 441 outputs the value of the byte coupled to the selected input port, and the byte values are then formed into the word to be read, i.e., ColMux 0 provides the first byte, ColMux 1 provides the second byte, ColMux 2 provides the third byte, and ColMux 3 provides the fourth byte.

In this embodiment, each input port of each column multiplexer 440, 441 is coupled to a different byte of the associated word as follows. For ColMux 0 in banks 510 and 511, input port 0 is coupled to b0 of word 0 of word lines 0, 1, etc., input port 1 is coupled to b1 of word 0 of word lines 0, 1, etc., input port 2 is coupled to b2 of word 0 of word lines 0, 1, etc., and input port 3 is coupled to b3 of word 0 of word lines 0, 1, etc. For ColMux 1 in banks 510 and 511, input port 0 is coupled to b0 of word 1 of word lines 0, 1, etc., input port 1 is coupled to b1 of word 1 of word lines 0, 1, etc., input port 2 is coupled to b2 of word 1 of word lines 0, 1, etc., and input port 3 is coupled to b3 of word 1 of word lines 0, 1, etc. For ColMux 2 in banks 510 and 511, input port 0 is coupled to b0 of word 2 of word lines 0, 1, etc., input port 1 is coupled to b1 of word 2 of word lines 0, 1, etc., input port 2 is coupled to b2 of word 2 of word lines 0, 1, etc., and input port 3 is coupled to b3 of word 2 of word lines 0, 1, etc. And, for ColMux 3 in banks 510 and 511, input port 0 is coupled to b0 of word 3 of word lines 0, 1, etc., input port 1 is coupled to b1 of word 3 of word lines 0, 1, etc., input port 2 is coupled to b2 of word 3 of word lines 0, 1, etc., and input port 3 is coupled to b3 of word 3 of word lines 0, 1, etc.

A BankSelect signal identifies which memory bank is to be selected for a read operation, i.e., a value of 0 selects bank 510 and a value of 1 selects bank 511.

As depicted in FIG. 6C, for illustration purposes, converted input data matrix 214 has been stored in word lines 410, 411 of banks 510, 511 of the memory according to data flow diagram 602.

FIG. 6D depicts a data flow diagram 603 for a sequence of read operations from a memory of an ANN accelerator, in accordance with an embodiment of the present disclosure.

Data flow diagram 603 is very similar to data flow diagram 502. The BankSelect signal of data flow diagram 603 replaces the ReadBankMuxSelect signal of data flow diagram 502, and the elements read from the respective the memories are the same. While data flow diagram 502 includes many read cycles that access banks 510 and 511 at the same time, data flow diagram 603 includes read cycles that only access one bank 510, 511 at a time.

For read cycles 1 to 4, the BankSelect signal is set to a value of 0 to access bank 510, and the WordLineSelect signal for bank 510 is set to a value of 0 to access word line 0.

The initial element of quadrant a_(q1) of converted input data matrix 214, i.e., element a₁, as well as elements x₁, y₂ and z₃, are read at the beginning of processing cycle 1, which corresponds to read cycle 1 depicted in FIG. 6D. Elements x₁, y₂ and z₃ may be read and not provided to MAC array 228, or the sense amplifiers associated with the column multiplexers for these elements may be disabled to prevent reading the memory cells in which these elements are stored. For read cycle 1, the ColMuxSelect signals for column multiplexers 440, 441 are set to a value of 0, and the following bytes are selected and read from the memory by column multiplexers 440 and/or column multiplexers 441: b0 of word 0 of word line 0 (i.e., a₁) by ColMux 0 of bank 510, b0 of word 1 of word line 0 (i.e., x₁) by ColMux 1 of bank 510, b0 of word 2 of word line 0 (i.e., y₂) by ColMux 2 of bank 510, and b0 of word 3 of word line 0 (i.e., z₃) by ColMux 3 of bank 510.

The next two elements of quadrant a_(q1) of converted input data matrix 214, i.e., elements a₂ and a₂, as well as elements x₂ and y₃, are read at the beginning of processing cycle 2, which corresponds to read cycle 2 depicted in FIG. 6D. Elements x₂ and y₃ may be read and not provided to MAC array 228, or the sense amplifiers associated with the column multiplexers for these elements may be disabled to prevent reading the memory cells in which these elements are stored. For read cycle 2, the ColMuxSelect signals for column multiplexers 440, 441 are set to a value of 1, and the following bytes are selected and read from the memory by column multiplexers 440 and/or column multiplexers 441: b1 of word 0 of word line 0 (i.e., a₂) by ColMux 0 of bank 510, b1 of word 1 of word line 0 (i.e., a₂) by ColMux 1 of bank 510, b1 of word 2 of word line 0 (i.e., x₂) by ColMux 2 of bank 510, and b1 of word 3 of word line 0 (i.e., y₃) by ColMux 3 of bank 510.

The next three elements of quadrant a_(q1) of converted input data matrix 214, i.e., elements a₆, a₃, and a₃, as well as element x₃, are read at the beginning of processing cycle 3, which corresponds to read cycle 3 depicted in FIG. 6D. As discussed above, element x₃ may be read and not provided to MAC array 228, or the sense amplifiers associated with the column multiplexers for this element may be disabled to prevent reading the memory cells in which this element are stored. For read cycle 3, the ColMuxSelect signals for column multiplexers 440, 441 are set to a value of 2, and the following bytes are selected and read from the memory by column multiplexers 440 and/or column multiplexers 441: b2 of word 0 of word line 0 (i.e., a₆) by ColMux 0 of bank 510, b2 of word 1 of word line 0 (i.e., a₃) by ColMux 1 of bank 510, b2 of word 2 of word line 0 (i.e., a₃) by ColMux 2 of bank 510, and b2 of word 3 of word line 0 (i.e., x₃) by ColMux 3 of bank 510.

The next four elements of quadrant a_(q1) of converted input data matrix 214, i.e., elements a₇, a₇, a₄ and a₄, are read at the beginning of processing cycle 4, which corresponds to read cycle 4 depicted in FIG. 6D. For read cycle 4, the ColMuxSelect signals for column multiplexers 440, 441 are set to a value of 3, and the following bytes are selected and read from the memory by column multiplexers 440 and/or column multiplexers 441: b₃ of word 0 of word line 0 (i.e., a₇) by ColMux 0 of bank 510, b₃ of word 1 of word line 0 (i.e., a₇) by ColMux 1 of bank 510, b₃ of word 2 of word line 0 (i.e., a₄) by ColMux 2 of bank 510, and b₃ of word 3 of word line 0 (i.e., a₄) by ColMux 3 of bank 510.

For read cycles 5 to 8, the BankSelect signal is set to a value of 1 to access bank 511, and the WordLineSelect signal for bank 511 is set to a value of 0 to access word line 0.

The first element of quadrant a_(q2) of converted input data matrix 214, i.e., element a₆, and the next three elements of quadrant a_(q1) of converted input data matrix 214, i.e., elements a₈, a₈ and a₈, are read at the beginning of processing cycle 5, which corresponds to read cycle 5 depicted in FIG. 6D. For read cycle 5, the ColMuxSelect signals for column multiplexers 440, 441 are set to a value of 0, and the following bytes are selected and read from the memory by column multiplexers 440 and/or column multiplexers 441: b0 of word 0 of word line 0 (i.e., a₆) by ColMux 0 of bank 511, b0 of word 1 of word line 0 (i.e., as) by ColMux 1 of bank 511, b0 of word 2 of word line 0 (i.e., as) by ColMux 2 of bank 511, and b0 of word 3 of word line 0 (i.e., a₅) by ColMux 3 of bank 511.

The next two elements of quadrant a_(q2) of converted input data matrix 214, i.e., elements a₇ and a₇, and the next two elements of quadrant a_(q1) of converted input data matrix 214, i.e., elements a₉ and a₉, are read at the beginning of processing cycle 6, which corresponds to read cycle 6 depicted in FIG. 6D. For read cycle 6, the ColMuxSelect signals for column multiplexers 440, 441 are set to a value of 1, and the following bytes are selected and read from the memory by column multiplexers 440 and/or column multiplexers 441: b1 of word 0 of word line 0 (i.e., a₇) by ColMux 0 of bank 511, b1 of word 1 of word line 0 (i.e., a₇) by ColMux 1 of bank 511, b1 of word 2 of word line 0 (i.e., a₉) by ColMux 2 of bank 511, and b1 of word 3 of word line 0 (i.e., a₉) by ColMux 3 of bank 511.

The next three elements of quadrant a_(q2) of converted input data matrix 214, i.e., elements a₁₁, a₈ and a₈, and the last element of quadrant a_(q1) of converted input data matrix 214, i.e., element a₁₀, are read at the beginning of processing cycle 7, which corresponds to read cycle 7 depicted in FIG. 6D. For read cycle 7, the ColMuxSelect signals for column multiplexers 440, 441 are set to a value of 2, and the following bytes are selected and read from the memory by column multiplexers 440 and/or column multiplexers 441: b2 of word 0 of word line 0 (i.e., a₁₁) by ColMux 0 of bank 511, b2 of word 1 of word line 0 (i.e., as) by ColMux 1 of bank 511, b2 of word 2 of word line 0 (i.e., as) by ColMux 2 of bank 511, and b2 of word 3 of word line 0 (i.e., a₁₀) by ColMux 3 of bank 511.

The next four elements of quadrant a_(q2) of converted input data matrix 214, i.e., elements a₁₂, a₁₂, a₉ and a₉, are read at the beginning of processing cycle 8, which corresponds to read cycle 8 depicted in FIG. 6D. For read cycle 8, the ColMuxSelect signals for column multiplexers 440, 441 are set to a value of 3, and the following bytes are selected and read from the memory by column multiplexers 440 and/or column multiplexers 441: b₃ of word 0 of word line 0 (i.e., a₁₂) by ColMux 0 of bank 511, b₃ of word 1 of word line 0 (i.e., a₁₂) by ColMux 1 of bank 511, b₃ of word 2 of word line 0 (i.e., a₉) by ColMux 2 of bank 511, and b₃ of word 3 of word line 0 (i.e., a₉) by ColMux 3 of bank 511.

For read cycles 9 to 12, the BankSelect signal is set to a value of 0 to access bank 510, and the WordLineSelect signal for bank 510 is set to a value of 1 to access word line 1.

The first element of quadrant a_(q3) of converted input data matrix 214, i.e., element a₁₁, and the next three elements of quadrant a_(q2) of converted input data matrix 214, i.e., elements a₁₃, a₁₃ and a₁₀, are read at the beginning of processing cycle 9, which corresponds to read cycle 9 depicted in FIG. 6D. For read cycle 9, the ColMuxSelect signals for column multiplexers 440, 441 are set to a value of 0, and the following bytes are selected and read from the memory by column multiplexers 440 and/or column multiplexers 441: b0 of word 0 of word line 1 (i.e., a₁₁) by ColMux 0 of bank 510, b0 of word 1 of word line 1 (i.e., a₁₃) by ColMux 1 of bank 511, b0 of word 2 of word line 1 (i.e., a₁₃) by ColMux 2 of bank 510, and b0 of word 3 of word line 1 (i.e., a₁₀) by ColMux 3 of bank 510.

The next two elements of quadrant a_(q3) of converted input data matrix 214, i.e., elements a₁₂ and a₁₂, and the next two elements of quadrant a_(q2) of converted input data matrix 214, i.e., elements a₁₄ and a₁₄, are read at the beginning of processing cycle 10, which corresponds to read cycle 10 depicted in FIG. 6D. For read cycle 10, the ColMuxSelect signals for column multiplexers 440, 441 are set to a value of 1, and the following bytes are selected and read from the memory by column multiplexers 440 and/or column multiplexers 441: b1 of word 0 of word line 1 (i.e., a₁₂) by ColMux 0 of bank 510, b1 of word 1 of word line 1 (i.e., a₁₂) by ColMux 1 of bank 510, b1 of word 2 of word line 1 (i.e., a₁₄) by ColMux 2 of bank 510, and b1 of word 3 of word line 1 (i.e., a₁₄) by ColMux 3 of bank 510.

The next three elements of quadrant a_(q3) of converted input data matrix 214, i.e., elements a₁₆, a₁₃ and a₁₃, and the last element of quadrant a_(q2) of converted input data matrix 214, i.e., element a₁₅, are read at the beginning of processing cycle 11, which corresponds to read cycle 11 depicted in FIG. 6D. For read cycle 11, the ColMuxSelect signals for column multiplexers 440, 441 are set to a value of 2, and the following bytes are selected and read from the memory by column multiplexers 440 and/or column multiplexers 441: b2 of word 0 of word line 1 (i.e., a₁₆) by ColMux 0 of bank 510, b2 of word 1 of word line 1 (i.e., a₁₃) by ColMux 1 of bank 510, b2 of word 2 of word line 1 (i.e., a₁₃) by ColMux 2 of bank 510, and b2 of word 3 of word line 1 (i.e., a₁₅) by ColMux 3 of bank 511.

The next four elements of quadrant a_(q3) of converted input data matrix 214, i.e., elements a₁₇, a₁₇, a₁₄ and a₁₄, are read at the beginning of processing cycle 12, which corresponds to read cycle 12 depicted in FIG. 6D. For read cycle 12, the ColMuxSelect signals for column multiplexers 440, 441 are set to a value of 3, and the following bytes are selected and read from the memory by column multiplexers 440 and/or column multiplexers 441: b₃ of word 0 of word line 1 (i.e., a₁₇) by ColMux 0 of bank 510, b₃ of word 1 of word line 1 (i.e., a₁₇) by ColMux 1 of bank 510, b₃ of word 2 of word line 1 (i.e., a₁₄) by ColMux 2 of bank 510, and b₃ of word 3 of word line 1 (i.e., a₁₄) by ColMux 3 of bank 510.

For read cycles 13 to 16, the BankSelect signal is set to a value of 1 to access bank 511, and the WordLineSelect signal for bank 511 is set to a value of 1 to access word line 1.

The first element of quadrant a_(q4) of converted input data matrix 214, i.e., element a₁₆, and the next three elements of quadrant a_(q3) of converted input data matrix 214, i.e., elements a₁₈, a₁₈ and a₁₅, are read at the beginning of processing cycle 13, which corresponds to read cycle 13 depicted in FIG. 6D. For read cycle 13, the ColMuxSelect signals for column multiplexers 440, 441 are set to a value of 0, and the following bytes are selected and read from the memory by column multiplexers 440 and/or column multiplexers 441: b0 of word 0 of word line 1 (i.e., a₁₆) by ColMux 0 of bank 511, b0 of word 1 of word line 1 (i.e., a₁₈) by ColMux 1 of bank 511, b0 of word 2 of word line 1 (i.e., a₁₈) by ColMux 2 of bank 511, and b0 of word 3 of word line 1 (i.e., a₁₅) by ColMux 3 of bank 511.

The next two elements of quadrant a_(q4) of converted input data matrix 214, i.e., elements a₁₇ and a₁₇, and the next two elements of quadrant a_(q3) of converted input data matrix 214, i.e., elements a₁₉ and a₁₉, are read at the beginning of processing cycle 14, which corresponds to read cycle 14 depicted in FIG. 6D. For read cycle 14, the ColMuxSelect signals for column multiplexers 440, 441 are set to a value of 1, and the following bytes are selected and read from the memory by column multiplexers 440 and/or column multiplexers 441: b1 of word 0 of word line 1 (i.e., a₁₇) by ColMux 0 of bank 511, b1 of word 1 of word line 1 (i.e., a₁₇) by ColMux 1 of bank 511, b1 of word 2 of word line 1 (i.e., a₁₉) by ColMux 2 of bank 511, and b1 of word 3 of word line 1 (i.e., a₁₉) by ColMux 3 of bank 511.

The next three elements of quadrant a_(q4) of converted input data matrix 214, i.e., elements a₂₁, a₁₈ and a₁₈, and the next element of quadrant a_(q3) of converted input data matrix 214, i.e., element a₂₀, are read at the beginning of processing cycle 15, which corresponds to read cycle 15 depicted in FIG. 6D. For read cycle 15, the ColMuxSelect signals for column multiplexers 440, 441 are set to a value of 2, and the following bytes are selected and read from the memory by column multiplexers 440 and/or column multiplexers 441: b2 of word 0 of word line 1 (i.e., a₂₁) by ColMux 0 of bank 511, b2 of word 1 of word line 1 (i.e., a₁₈) by ColMux 1 of bank 511, b2 of word 2 of word line 1 (i.e., a₁₈) by ColMux 2 of bank 511, and b2 of word 3 of word line 1 (i.e., a₂₀) by ColMux 3 of bank 511.

The next four elements of quadrant a_(q4) of converted input data matrix 214, i.e., elements a₂₂, a₂₂, a₁₉ and a₁₉, are read at the beginning of processing cycle 16, which corresponds to read cycle 16 depicted in FIG. 6D. For read cycle 16, the ColMuxSelect signals for column multiplexers 440, 441 are set to a value of 3, and the following bytes are selected and read from the memory by column multiplexers 440 and/or column multiplexers 441: b₃ of word 0 of word line 1 (i.e., a₂₂) by ColMux 0 of bank 511, b₃ of word 1 of word line 1 (i.e., a₂₂) by ColMux 1 of bank 511, b₃ of word 2 of word line 1 (i.e., a₁₉) by ColMux 2 of bank 511, and b₃ of word 3 of word line 1 (i.e., a₁₉) by ColMux 3 of bank 511.

For read cycles 17 to 19, the BankSelect signal is set to a value of 0 to access bank 510, and the WordLineSelect signal for bank 510 is set to a value of 2 to access word line 2 (not depicted in FIG. 6C).

The first element of quadrant b_(q1) (not depicted) of the next converted input data matrix 214 (not depicted), i.e., element b₁, and the next three elements of quadrant a_(q4) of converted input data matrix 214, i.e., elements a₂₃, a₂₃ and a₂₀, are read at the beginning of processing cycle 17, which corresponds to read cycle 17 depicted in FIG. 6D. For read cycle 17, the ColMuxSelect signals for column multiplexers 440, 441 are set to a value of 0, and the following bytes are selected and read from the memory by column multiplexers 440 and/or column multiplexers 441: b0 of word 0 of word line 2 (i.e., b₁) by ColMux 0 of bank 510, b0 of word 1 of word line 2 (i.e., a₂₃) by ColMux 1 of bank 510, b0 of word 2 of word line 2 (i.e., a₂₃) by ColMux 2 of bank 510, and b0 of word 3 of word line 2 (i.e., a₂₀) by ColMux 3 of bank 510.

The next two elements of quadrant b_(q1) of the next converted input data matrix 214, i.e., elements b2 and b2, and the next two elements of quadrant a_(q4) of converted input data matrix 214, i.e., elements a₂₄ and a₂₄, are read at the beginning of processing cycle 18, which corresponds to read cycle 18 depicted in FIG. 6D. For read cycle 18, the ColMuxSelect signals for column multiplexers 440, 441 are set to a value of 1, and the following bytes are selected and read from the memory by column multiplexers 440 and/or column multiplexers 441: b1 of word 0 of word line 2 (i.e., b2) by ColMux 0 of bank 510, b1 of word 1 of word line 2 (i.e., b2) by ColMux 1 of bank 510, b1 of word 2 of word line 2 (i.e., a₂₄) by ColMux 2 of bank 510, and b1 of word 3 of word line 2 (i.e., a₂₄) by ColMux 3 of bank 510.

The next three elements of quadrant b_(q1) of the next converted input data matrix 214, i.e., elements b6, b₃ and b₃, and the last element of quadrant a_(q4) of converted input data matrix 214, i.e., element a₂₅, are read at the beginning of processing cycle 19, which corresponds to read cycle 19 depicted in FIG. 6D. For read cycle 19, the ColMuxSelect signals for column multiplexers 440, 441 are set to a value of 2, and the following bytes are selected and read from the memory by column multiplexers 440 and/or column multiplexers 441: b2 of word 0 of word line 2 (i.e., b6) by ColMux 0 of bank 510, b2 of word 1 of word line 2 (i.e., b₃) by ColMux 1 of bank 510, b2 of word 2 of word line 2 (i.e., b₃) by ColMux 2 of bank 510, and b2 of word 3 of word line 1 (i.e., a₂₅) by ColMux 3 of bank 510.

And so on.

FIG. 6E depicts a word selector or multiplexer mapping diagram 604 for a memory for an ANN accelerator, in accordance with an embodiment of the present disclosure.

As described above, bank 510 and 511 of the memory may include four column multiplexers 440 and 441 (respectively) associated with read operations, and four column multiplexers 450 and 451 (respectively) associated with write operations. Multiplexer mapping diagram 604 illustrates the mapping between the “read” ColMuxSelect signal values (i.e., 0, 1, 2 and 3) and the bytes 330 of each word 320, as well as the mapping between the “write” ColMuxSelect signal values (i.e., 0, 1, 2 and 3) and the bytes 330 of each word 320.

A “read” ColMuxSelect signal value of 0 selects input port 0 of each column multiplexer 440, 441, and, as illustrated in FIG. 6E, each input port 0 of each column multiplexer 440, 441 is coupled 442 to byte 0 of word 0, 1, 2 or 3. A “read” ColMuxSelect signal value of 1 selects input port 1 of each column multiplexer 440, 441, and each input port 1 of each column multiplexer 440, 441 is coupled 442 to byte 1 of word 0, 1, 2 or 3. A “read” ColMuxSelect signal value of 2 selects input port 2 of each column multiplexer 440, 441, and each input port 2 of each column multiplexer 440, 441 is coupled 442 to byte 2 of word 0, 1, 2 or 3. And, a “read” ColMuxSelect signal value of 3 selects input port 3 of each column multiplexer 440, 441, and each input port 3 of each column multiplexer 440, 441 is coupled 442 to byte 3 of word 0, 1, 2 or 3.

A “write” ColMuxSelect signal value of 0 selects input port 0 of column multiplexers 440, 441. Input port 0 of the first column multiplexer 440, 441 (i.e., ColMux 0) is coupled 442 to byte 0 of word 0, input port 0 of the second column multiplexer 440, 441 (i.e., ColMux 1) is coupled 442 to byte 1 of word 1, input port 0 of the third column multiplexer 440, 441 (i.e., ColMux 2) is coupled 442 to byte 2 of word 2, and input port 0 of the fourth column multiplexer 440, 441 (i.e., ColMux 3) is coupled 442 to byte 3 of word 3.

A “write” ColMuxSelect signal value of 1 selects input port 1 of each column multiplexer 440, 441. Input port 1 of the first column multiplexer 440, 441 (i.e., ColMux 0) is coupled 442 to byte 1 of word 0, input port 1 of the second column multiplexer 440, 441 (i.e., ColMux 1) is coupled 442 to byte 2 of word 1, input port 1 of the third column multiplexer 440, 441 (i.e., ColMux 2) is coupled 442 to byte 3 of word 2, and input port 1 of the fourth column multiplexer 440, 441 (i.e., ColMux 3) is coupled 442 to byte 0 of word 3.

A “write” ColMuxSelect signal value of 2 selects input port 2 of each column multiplexer 440, 441. Input port 2 of the first column multiplexer 440, 441 (i.e., ColMux 0) is coupled 442 to byte 2 of word 0, input port 2 of the second column multiplexer 440, 441 (i.e., ColMux 1) is coupled 442 to byte 3 of word 1, input port 2 of the third column multiplexer 440, 441 (i.e., ColMux 2) is coupled 442 to byte 0 of word 2, and input port 2 of the fourth column multiplexer 440, 441 (i.e., ColMux 3) is coupled 442 to byte 1 of word 3.

A “write” ColMuxSelect signal value of 3 selects input port 3 of each column multiplexer 440, 441. Input port 3 of the first column multiplexer 440, 441 (i.e., ColMux 0) is coupled 442 to byte 3 of word 0, input port 3 of the second column multiplexer 440, 441 (i.e., ColMux 1) is coupled 442 to byte 0 of word 1, input port 3 of the third column multiplexer 440, 441 (i.e., ColMux 2) is coupled 442 to byte 1 of word 2, and input port 3 of the fourth column multiplexer 440, 441 (i.e., ColMux 3) is coupled 442 to byte 2 of word 3.

In many situations, the power associated with skewing the data to be written (as described in this embodiment) may be significantly lower than the power associated with skewing the data to be read (in the embodiments described above) because write operations may be less frequent than read operations. Additionally, while saving extra power in skewed read operations may require additional circuitry to disable the sense amplifiers (as described above), saving extra power in skewed write operations, by blocking unwanted write operations (i.e., writing elements x₁, x₂, x₃, y₂, y₃, z₃), may be straightforward using the bit-mask pin (e.g., the “MASK” or “WEN” pin). And, the power savings due to blocked write operations may save about 50%.

In other embodiments, backward compatibility for “un-skewed” read and write operations may be provided by adding a bank of delay registers or flip flop blocks after the output of the read-skewing memory or before the input of the write-skewing memory to “un-skew” the data. While the area savings may be lost, power is still saved during read-skewing or write-skewing operations because the delay registers or flip flop blocks are not activated. For example, a bypass path may be activated in “skewing mode” to bypass the delay registers or flip flop blocks, and deactivated in “backward compatibility mode” to ensure that the data flows through the delay registers or flip flop blocks.

FIG. 7 depicts a block diagram of system 100, in accordance with an embodiment of the present disclosure.

Computer 102 includes communication bus 110 coupled to one or more processors 120, memory 130, I/O interfaces 140, display interface 150, one or more communication interfaces 160 and one or more ANN accelerators 170. Generally, I/O interfaces 140 are coupled to I/O devices 142 using a wired or wireless connection display interface 150 is coupled to display 152, and communication interface 160 is connected to network 162 using a wired or wireless connection.

Communication bus 110 is a communication system that transfers data between processor 120, memory 130, I/O interfaces 140, display interface 150, communication interface 160, ANN accelerator 170, as well as other components not depicted. Power connector 112 is coupled to communication bus 110 and a power supply (not shown).

Processor 120 includes one or more general-purpose or application-specific microprocessors that executes instructions to perform control, computation, input/output, etc. functions for computer 102. Processor 120 may include a single integrated circuit, such as a micro-processing device, or multiple integrated circuit devices and/or circuit boards working in cooperation to accomplish the functions of processor 120. In addition, processor 120 may execute computer programs or modules, such as operating system 132, software modules 134, etc., stored within memory 130. For example, software modules 134 may include an ML application, an ANN application, a CNN application, etc.

Generally, storage element or memory 130 stores instructions for execution by processor 120 and data. Memory 130 may include a variety of non-transitory computer-readable medium that may be accessed by processor 120. In various embodiments, memory 130 may include volatile and nonvolatile medium, non-removable medium and/or removable medium. For example, memory 130 may include any combination of random access memory (RAM), dynamic RAM (DRAM), static RAM (SRAM), read only memory (ROM), flash memory, cache memory, and/or any other type of non-transitory computer-readable medium.

Memory 130 contains various components for retrieving, presenting, modifying, and storing data. For example, memory 130 stores software modules that provide functionality when executed by processor 120. The software modules include operating system 132 that provides operating system functionality for computer 102. Software modules 134 provide various functionality, such as image classification using convolutional neural networks, etc. Data 136 may include data associated with operating system 132, software modules 134, etc.

I/O interfaces 140 are configured to transmit and/or receive data from I/O devices 142. I/O interfaces 140 enable connectivity between processor 120 and 1/O devices 142 by encoding data to be sent from processor 120 to I/O devices 142, and decoding data received from I/O devices 142 for processor 120. Generally, data may be sent over wired and/or wireless connections. For example, I/O interfaces 140 may include one or more wired communications interfaces, such as USB, Ethernet, etc., and/or one or more wireless communications interfaces, coupled to one or more antennas, such as WiFi, Bluetooth, cellular, etc.

Generally, I/O devices 142 provide input to computer 102 and/or output from computer 102. As discussed above, I/O devices 142 are operably connected to computer 102 using a wired and/or wireless connection. I/O devices 142 may include a local processor coupled to a communication interface that is configured to communicate with computer 102 using the wired and/or wireless connection. For example, I/O devices 142 may include a keyboard, mouse, touch pad, joystick, etc.

Display interface 150 is configured to transmit image data from computer 102 to monitor or display 152.

Communication interface 160 is configured to transmit data to and from network 162 using one or more wired and/or wireless connections. Network 162 may include one or more local area networks, wide area networks, the Internet, etc., which may execute various network protocols, such as, for example, wired and/or wireless Ethernet, Bluetooth, etc. Network 162 may also include various combinations of wired and/or wireless physical layers, such as, for example, copper wire or coaxial cable networks, fiber optic networks, Bluetooth wireless networks, WiFi wireless networks, CDMA, FDMA and TDMA cellular wireless networks, etc.

FIG. 8 depicts an ANN accelerator 170, in accordance with an embodiment of the present disclosure.

ANN accelerator 170 is configured to execute machine learning models, such as, for example, ANNs, CNNs, RNNs, etc., in support of various applications embodied by software modules 134. Generally, ANN accelerator 170 may include one or more processors, coprocessors, processing engines (PEs), compute engines (CEs), etc., such as, for example, CPUs, MCUs, GPUs, NPUs, such as, for example, the ARM Machine Learning (ML) Processor, DSPs, field programmable gate arrays (FPGAs), application specific integrated circuits (ASICs), controllers, microcontrollers, matrix multiplier circuits, MAC arrays, etc. Generally, ANN accelerator 170 receives input data from memory 130 over communication bus 110, and transmits output data to memory 130 over communication bus 110.

ANN accelerator 170 also includes controller 172, communications bus interface 174, and one or more non-volatile and/or volatile memories 176, such as, for example, ROM, flash memory, SRAM, DRAM, etc. Controller 172 is coupled to communication bus interface 174, memory 176 and one or more compute engines (CEs) 180, and generally controls the functionality, data flow, etc., of ANN accelerator 170. Memory 176 is coupled to communication bus interface 174 and CEs 180, and stores, inter alia, ANN weights and activations. Each CE 180 includes one or more MAC arrays 182, and each MAC array 182 includes a number of MAC units, such as, for example, 4 MAC units, 8 MAC units, 16 MAC units (m₁ to m₁₆, as depicted in FIG. 8 ), 32 MAC units, etc.

Embodiments of the present disclosure advantageously eliminate the delay registers or flip flop blocks by changing the way data is read from, or written to, the memory without adding complexity and area to SRAM memories.

The embodiments described herein are combinable.

In one embodiment, a memory for an ANN accelerator includes a first bank, a second bank and a bank selector. The first bank includes at least two word lines and a plurality of read word selectors, each word line stores a plurality of words, each word has a plurality of bytes, each read word selector has a plurality of input ports and an output port, each read word selector is coupled to a corresponding word in each word line, and each read word selector is configured to select a byte of the corresponding word of a selected word line based on a byte select signal. The second bank includes at least two word lines and a plurality of read word selectors, each word line stores a plurality of words, each word has a plurality of bytes, each read word selector has a plurality of input ports and an output port, each read word selector is coupled to a corresponding word in each word line, and each read word selector is configured to select a byte of the corresponding word of a selected word line based on the byte select signal. The bank selector is coupled to the outputs of the read word selectors of the first bank and the outputs of the read word selectors of the second bank, and is configured to select a combination of read word selectors from at least one of the first bank and the second bank based on a bank select signal.

In another embodiment of the memory, the first bank is configured to select a word line based on a first word line select signal, and the second bank is configured to select a word line based on a second word line select signal.

In another embodiment of the memory, the read word selectors are column multiplexers and the byte select signal is a column multiplexer select signal; and the bank selector is a bank multiplexer and the bank select signal is a bank multiplexer select signal.

In another embodiment of the memory, each column multiplexer input port is coupled to a different byte of the corresponding word; and the bank multiplexer includes a plurality of read multiplexers, each read multiplexer includes a first input port, a second input port and an output port, the first input port is coupled to an output port of a column multiplexer in the first bank, and the second input port is coupled to an output port of a corresponding column multiplexer in the second bank.

In another embodiment of the memory, for the first bank, the input ports of each column multiplexer are coupled to a unique sequence of bytes of the corresponding word; and for the second bank, the input ports of each column multiplexer are coupled to the unique sequence of bytes of the corresponding column multiplexer in the first bank.

In another embodiment of the memory, for the first bank, a first input port of a first column multiplexer is coupled to a first byte of the corresponding word, and the first input ports of the remaining column multiplexers are not coupled to a first byte of the corresponding words; and for the second bank, a first input port of a first column multiplexer is coupled to a first byte of the corresponding word, and the first input ports of the remaining column multiplexers are not coupled to a first byte of the corresponding words.

In another embodiment of the memory, each word includes four bytes, and each byte includes eight bits; the first bank includes four column multiplexers, the second bank includes four column multiplexers, and each column multiplexer includes four 8-bit input ports and one 8-bit output port; and the bank multiplexer includes four read multiplexers, and each read multiplexer includes two 8-bit input ports and one 8-bit output port.

In another embodiment of the memory, the column multiplexer select signal has four values; and the bank multiplexer select signal has four bits.

In another embodiment of the memory, read a sequence of bytes by the combination of read word selectors; and form the sequence of bytes into an output word.

In another embodiment of the memory, the bank selector is further configured to send the output word to a systolic MAC array.

In one embodiment, a method for reading from a memory of an ANN accelerator is provided. In response to receiving a first word line select signal at a first bank, a word line is selected based on the first word line select signal, the first bank having at least two word lines and a plurality of read word selectors, each word line storing a plurality of words, each word having a plurality of bytes, each read word selector having a plurality of input ports and an output port, and each read word selector coupled to a corresponding word in each word line. In response to receiving a second word line select signal at a second bank, a word line is selected based on the second word line select signal, the second bank having at least two word lines and a plurality of read word selectors, each word line storing a plurality of words, each word having a plurality of bytes, each read word selector having a plurality of input ports and an output port, and each read word selector coupled to a corresponding word in each word line. In response to receiving a byte select signal at each read word selector, a byte of the corresponding word of a selected word line is selected based on the byte select signal. In response to receiving a bank select signal at a bank selector coupled to the first bank and the second bank, a combination of read word selectors from at least one of the first bank and the second bank is selected based on the bank select signal. A sequence of bytes is read by the combination of read word selectors, and the sequence of bytes is formed into an output word by the bank selector.

In another embodiment of the method, the method further comprises sending the output word to a systolic MAC array.

In another embodiment of the method, the first bank is configured to select a word line based on a first word line select signal, and the second bank is configured to select a word line based on a second word line select signal.

In another embodiment of the method, the read word selectors are column multiplexers and the byte select signal is a column multiplexer select signal; and the bank selector is a bank multiplexer and the bank select signal is a bank multiplexer select signal.

In another embodiment of the method, each column multiplexer input port is coupled to a different byte of the corresponding word; and the bank multiplexer includes a plurality of read multiplexers, each read multiplexer includes a first input port, a second input port and an output port, the first input port is coupled to an output port of a column multiplexer in the first bank, and the second input port is coupled to an output port of a corresponding column multiplexer in the second bank.

In another embodiment of the method, for the first bank, the input ports of each column multiplexer are coupled to a unique sequence of bytes of the corresponding word; and for the second bank, the input ports of each column multiplexer are coupled to the unique sequence of bytes of the corresponding column multiplexer in the first bank.

In another embodiment of the method, for the first bank, a first input port of a first column multiplexer is coupled to a first byte of the corresponding word, and the first input ports of the remaining column multiplexers are not coupled to a first byte of the corresponding words; and for the second bank, a first input port of a first column multiplexer is coupled to a first byte of the corresponding word, and the first input ports of the remaining column multiplexers are not coupled to a first byte of the corresponding words.

In another embodiment of the method, each word includes four bytes, and each byte includes eight bits; the first bank includes four column multiplexers, the second bank includes four column multiplexers, and each column multiplexer includes four 8-bit input ports and one 8-bit output port; and the bank multiplexer includes four read multiplexers, and each read multiplexer includes two 8-bit input ports and one 8-bit output port.

In another embodiment of the method, the column multiplexer select signal has four values; and the bank multiplexer select signal has four bits.

In another embodiment of the method, a first input port of a second column multiplexer is coupled to a fourth byte of the corresponding word; a first input port of a third column multiplexer is coupled to a third byte of the corresponding word; and a first input port of a fourth column multiplexer is coupled to a second byte of the corresponding word.

While implementations of the disclosure are susceptible to embodiment in many different forms, there is shown in the drawings and will herein be described in detail specific embodiments, with the understanding that the present disclosure is to be considered as an example of the principles of the disclosure and not intended to limit the disclosure to the specific embodiments shown and described. In the description above, like reference numerals may be used to describe the same, similar or corresponding parts in the several views of the drawings.

In this document, relational terms such as first and second, top and bottom, and the like may be used solely to distinguish one entity or action from another entity or action without necessarily requiring or implying any actual such relationship or order between such entities or actions. The terms “comprises,” “comprising,” “includes,” “including,” “has,” “having,” or any other variations thereof, are intended to cover a non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements does not include only those elements but may include other elements not expressly listed or inherent to such process, method, article, or apparatus. An element preceded by “comprises . . . a” does not, without more constraints, preclude the existence of additional identical elements in the process, method, article, or apparatus that comprises the element.

Reference throughout this document to “one embodiment,” “certain embodiments,” “an embodiment,” “implementation(s),” “aspect(s),” or similar terms means that a particular feature, structure, or characteristic described in connection with the embodiment is included in at least one embodiment of the present disclosure. Thus, the appearances of such phrases or in various places throughout this specification are not necessarily all referring to the same embodiment. Furthermore, the particular features, structures, or characteristics may be combined in any suitable manner in one or more embodiments without limitation.

The term “or” as used herein is to be interpreted as an inclusive or meaning any one or any combination. Therefore, “A, B or C” means “any of the following: A; B; C; A and B; A and C; B and C; A, B and C.” An exception to this definition will occur only when a combination of elements, functions, steps or acts are in some way inherently mutually exclusive. Also, grammatical conjunctions are intended to express any and all disjunctive and conjunctive combinations of conjoined clauses, sentences, words, and the like, unless otherwise stated or clear from the context. Thus, the term “or” should generally be understood to mean “and/or” and so forth. References to items in the singular should be understood to include items in the plural, and vice versa, unless explicitly stated otherwise or clear from the text.

Recitation of ranges of values herein are not intended to be limiting, referring instead individually to any and all values falling within the range, unless otherwise indicated, and each separate value within such a range is incorporated into the specification as if it were individually recited herein. The words “about,” “approximately,” or the like, when accompanying a numerical value, are to be construed as indicating a deviation as would be appreciated by one of ordinary skill in the art to operate satisfactorily for an intended purpose. Ranges of values and/or numeric values are provided herein as examples only, and do not constitute a limitation on the scope of the described embodiments. The use of any and all examples, or exemplary language (“e.g.,” “such as,” “for example,” or the like) provided herein, is intended merely to better illuminate the embodiments and does not pose a limitation on the scope of the embodiments. No language in the specification should be construed as indicating any unclaimed element as essential to the practice of the embodiments.

For simplicity and clarity of illustration, reference numerals may be repeated among the figures to indicate corresponding or analogous elements. Numerous details are set forth to provide an understanding of the embodiments described herein. The embodiments may be practiced without these details. In other instances, well-known methods, procedures, and components have not been described in detail to avoid obscuring the embodiments described. The description is not to be considered as limited to the scope of the embodiments described herein.

In the following description, it is understood that terms such as “first,” “second,” “top,” “bottom,” “up,” “down,” “above,” “below,” and the like, are words of convenience and are not to be construed as limiting terms. Also, the terms apparatus, device, system, etc. may be used interchangeably in this text.

The many features and advantages of the disclosure are apparent from the detailed specification, and, thus, it is intended by the appended claims to cover all such features and advantages of the disclosure which fall within the scope of the disclosure. Further, since numerous modifications and variations will readily occur to those skilled in the art, it is not desired to limit the disclosure to the exact construction and operation illustrated and described, and, accordingly, all suitable modifications and equivalents may be resorted to that fall within the scope of the disclosure. 

What is claimed is:
 1. A multi-bank memory for an artificial neural network (ANN) accelerator, comprising: a first bank including at least two word lines and a plurality of read word selectors, each word line storing a plurality of words, each word having a plurality of bytes, each read word selector having a plurality of input ports and an output port, where each read word selector is coupled to a corresponding word in each word line, each read word selector is configured to select a byte of the corresponding word of a selected word line based on a byte select signal, and each value of the byte select signal is mapped to a different byte of each corresponding word in the selected word line; a second bank including at least two word lines and a plurality of read word selectors, each word line storing a plurality of words, each word having a plurality of bytes, each read word selector having a plurality of input ports and an output port, where each read word selector is coupled to a corresponding word in each word line, and each read word selector is configured to select a byte of the corresponding word of a selected word line based on the byte select signal; and a bank selector, coupled to the outputs of the read word selectors of the first bank and the outputs of the read word selectors of the second bank, configured to select a combination of read word selectors from at least one of the first bank and the second bank based on a bank select signal.
 2. The multi-bank memory of claim 1, where the first bank is configured to select a word line based on a first word line select signal, and the second bank is configured to select a word line based on a second word line select signal.
 3. The multi-bank memory of claim 2, where: the read word selectors are column multiplexers and the byte select signal is a column multiplexer select signal; and the bank selector is a bank multiplexer and the bank select signal is a bank multiplexer select signal.
 4. The multi-bank memory of claim 3, where: each column multiplexer input port is coupled to a different byte of the corresponding word; and the bank multiplexer includes a plurality of read multiplexers, each read multiplexer includes a first input port, a second input port and an output port, the first input port is coupled to an output port of a column multiplexer in the first bank, and the second input port is coupled to an output port of a corresponding column multiplexer in the second bank.
 5. The multi-bank memory of claim 4, where: for the first bank, the input ports of each column multiplexer are coupled to a unique sequence of bytes of the corresponding word; and for the second bank, the input ports of each column multiplexer are coupled to the unique sequence of bytes of the corresponding column multiplexer in the first bank.
 6. The multi-bank memory of claim 5, where: for the first bank, a first input port of a first column multiplexer is coupled to a first byte of the corresponding word, and the first input ports of the remaining column multiplexers are not coupled to a first byte of the corresponding words; and for the second bank, a first input port of a first column multiplexer is coupled to a first byte of the corresponding word, and the first input ports of the remaining column multiplexers are not coupled to a first byte of the corresponding words.
 7. The multi-bank memory of claim 4, where: each word includes four bytes, and each byte includes eight bits; the first bank includes four column multiplexers, the second bank includes four column multiplexers, and each column multiplexer includes four 8-bit input ports and one 8-bit output port; and the bank multiplexer includes four read multiplexers, and each read multiplexer includes two 8-bit input ports and one 8-bit output port.
 8. The multi-bank memory of claim 7, where: the column multiplexer select signal has four values; and the bank multiplexer select signal has four bits.
 9. The multi-bank memory of claim 1, where the bank selector is further configured to: read a sequence of bytes by the combination of read word selectors; and form the sequence of bytes into an output word.
 10. The multi-bank memory of claim 9, where the bank selector is further configured to: send the output word to a systolic multiply-and-accumulate (MAC) array.
 11. A method for reading from a multi-bank memory of an artificial neural network (ANN) accelerator, comprising: in response to receiving a first word line select signal at a first bank, selecting a word line based on the first word line select signal, the first bank having at least two word lines and a plurality of read word selectors, each word line storing a plurality of words, each word having a plurality of bytes, each read word selector having a plurality of input ports and an output port, and each read word selector coupled to a corresponding word in each word line; in response to receiving a second word line select signal at a second bank, selecting a word line based on the second word line select signal, the second bank having at least two word lines and a plurality of read word selectors, each word line storing a plurality of words, each word having a plurality of bytes, each read word selector having a plurality of input ports and an output port, and each read word selector coupled to a corresponding word in each word line; in response to receiving a byte select signal at each read word selector, selecting a byte of the corresponding word of a selected word line based on the byte select signal, where each value of the byte select signal is mapped to a different byte of each corresponding word in the selected word line; in response to receiving a bank select signal at a bank selector coupled to the first bank and the second bank, selecting a combination of read word selectors from at least one of the first bank and the second bank based on the bank select signal; reading a sequence of bytes by the combination of read word selectors; and forming the sequence of bytes into an output word by the bank selector.
 12. The method of claim 11, where the first bank is configured to select a word line based on a first word line select signal, and the second bank is configured to select a word line based on a second word line select signal.
 13. The method of claim 12, where: the read word selectors are column multiplexers and the byte select signal is a column multiplexer select signal; and the bank selector is a bank multiplexer and the bank select signal is a bank multiplexer select signal.
 14. The method of claim 13, where: each column multiplexer input port is coupled to a different byte of the corresponding word; and the bank multiplexer includes a plurality of read multiplexers, each read multiplexer includes a first input port, a second input port and an output port, the first input port is coupled to an output port of a column multiplexer in the first bank, and the second input port is coupled to an output port of a corresponding column multiplexer in the second bank.
 15. The method of claim 14, where: for the first bank, the input ports of each column multiplexer are coupled to a unique sequence of bytes of the corresponding word; and for the second bank, the input ports of each column multiplexer are coupled to the unique sequence of bytes of the corresponding column multiplexer in the first bank.
 16. The method of claim 15, where: for the first bank, a first input port of a first column multiplexer is coupled to a first byte of the corresponding word, and the first input ports of the remaining column multiplexers are not coupled to a first byte of the corresponding words; and for the second bank, a first input port of a first column multiplexer is coupled to a first byte of the corresponding word, and the first input ports of the remaining column multiplexers are not coupled to a first byte of the corresponding words.
 17. The method of claim 16, where: each word includes four bytes, and each byte includes eight bits; the first bank includes four column multiplexers, the second bank includes four column multiplexers, and each column multiplexer includes four 8-bit input ports and one 8-bit output port; and the bank multiplexer includes four read multiplexers, and each read multiplexer includes two 8-bit input ports and one 8-bit output port.
 18. The method of claim 17, where: the column multiplexer select signal has four values; and the bank multiplexer select signal has four bits.
 19. The method of claim 17, where: a first input port of a second column multiplexer is coupled to a fourth byte of the corresponding word; a first input port of a third column multiplexer is coupled to a third byte of the corresponding word; and a first input port of a fourth column multiplexer is coupled to a second byte of the corresponding word.
 20. A memory bank, comprising: at least two word lines, each word line storing a plurality of words, each word having a plurality of bytes; and a plurality of read word selectors, each read word selector having a plurality of input ports and an output port, where: each read word selector is coupled to a corresponding word in each word line, each read word selector is configured to select a byte of the corresponding word of a selected word line based on a byte select signal, and each value of the byte select signal is mapped to a different byte of each corresponding word in the selected word line. 